Ceramic anion exchange materials

ABSTRACT

Anion exchange membranes and materials including silica-based ceramics, and associated methods, are provided. In some aspects, anion exchange membranes that include a silica-based ceramic that forms a coating on and/or within a porous support membrane are described. The anion exchange membranes and materials may have certain structural or chemical attributes (e.g., pore size/distribution, chemical functionalization) that, alone or in combination, can result in advantageous performance characteristics in any of a variety of applications for which selective transport of positively charged ions through membranes/materials is desired. In some embodiments, the silica-based ceramic contains relatively small pores (e.g., substantially spherical nanopores) that may contribute to some such advantageous properties. In some embodiments, the anion exchange membrane or material includes quaternary ammonium groups covalently bound to the silica-based ceramic.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Application Ser. No. 62/857,227, filed Jun. 4, 2019, andentitled “CERAMIC ANION EXCHANGE MATERIALS,” which is incorporatedherein by reference in its entirety for all purposes.

TECHNICAL FIELD

Ion exchange membranes and materials, and associated methods, aregenerally described.

BACKGROUND

Anion exchange membranes and materials are used in a variety ofindustrial applications where the selective transport of negativelycharged ions is desired. In the case of anion exchange membranes,negatively charged ions can be selectively transported through themembrane cross-section. One type of anion exchange membrane is ahydroxide ion exchange membrane, though anion exchange membranes capableof the selective transport of other types of negatively charged ionsexist. Certain embodiments of the present disclosure are directed toinventive compositions, membranes, and materials, and related methods,for improving the performance and/or properties of anion exchangemembranes and materials.

SUMMARY

Anion exchange membranes and materials including silica-based ceramics,and associated methods, are generally described. The subject matter ofthe present invention involves, in some cases, interrelated products,alternative solutions to a particular problem, and/or a plurality ofdifferent uses of one or more systems and/or articles.

In one aspect, anion exchange membranes are provided. In someembodiments, the anion exchange membrane comprises a porous supportmembrane and a silica-based ceramic that coats at least a portion of theporous support membrane. The silica-based ceramic comprises quaternaryammonium groups covalently bound to the silica-based ceramic. Thesilica-based ceramic has an average pore diameter of less than or equalto 10 nm.

In some embodiments, the anion exchange membrane comprises a poroussupport membrane and a silica-based ceramic that forms a coating onand/or within the porous support membrane. The silica-based ceramiccomprises quaternary ammonium groups covalently bound to thesilica-based ceramic. The anion exchange membrane has a chloride ionconductivity of greater than or equal to 0.00001 S/cm.

In some embodiments, the anion exchange membrane comprises asilica-based ceramic, and the anion exchange membrane has a water uptakeof greater than or equal to 10 wt % and a linear expansion of less thanor equal to 10%.

In some embodiments, the anion exchange membrane comprises a poroussupport membrane and a silica-based ceramic that forms a coating onand/or within the porous support membrane. The silica-based ceramiccomprises quaternary ammonium groups covalently bound to thesilica-based ceramic. The quaternary ammonium groups are directlyadjacent to a surface of the porous support membrane.

In some embodiments, the anion exchange membrane comprises a poroussupport membrane and a silica-based ceramic that coats at least aportion of the porous support membrane. The silica-based ceramiccomprises quaternary ammonium groups covalently bound to thesilica-based ceramic. Greater than or equal to 50% of the pore volume ofthe porous support membrane is filled by the silica-based ceramic.

In some embodiments, the anion exchange membrane comprises a poroussupport membrane and a silica-based ceramic that forms a coating onand/or within the porous support membrane. The silica-based ceramiccomprises quaternary ammonium groups covalently bound to thesilica-based ceramic. The anion exchange membrane has an anion exchangecapacity of greater than or equal to 0.01 meq/g.

In some embodiments, the anion exchange membrane comprises a poroussupport membrane and a silica-based ceramic that coats at least aportion of the porous support membrane. The silica-based ceramiccomprises quaternary ammonium groups covalently bound to thesilica-based ceramic. The quaternary ammonium groups are present in theanion exchange membrane in an amount of greater than or equal to 0.01mmol per gram of the anion exchange membrane.

In some embodiments, an anion exchange material is provided. The anionexchange material comprises a silica-based ceramic that comprisesquaternary ammonium groups covalently bound to the silica-based ceramic.The silica-based ceramic comprises Si in an amount greater than or equalto 6 wt % of the silica-based ceramic. The anion exchange material hasan anion exchange capacity of greater than or equal to 0.01 meq/g. Thesilica-based ceramic has an average pore diameter of less than 10 nm.

In some embodiments, an anion exchange membrane is provided. In someembodiments, the anion exchange membrane comprises a silica-basedceramic comprising Si in an amount greater than or equal to 6 wt % ofthe silica-based ceramic. The anion exchange membrane has an anionexchange capacity of greater than or equal to 0.01 meq/g.

In some embodiments, the anion exchange membrane comprises asilica-based ceramic. The anion exchange membrane has an anion exchangecapacity of greater than or equal to 0.01 meq/g and a linear expansionof less than or equal to 10%.

In some embodiments, an anion exchange membrane is provided. The anionexchange membrane comprises a silica-based ceramic comprising Si in anamount greater than or equal to 6 wt % of the silica-based ceramic. Theanion exchange membrane has an anion permselectivity of greater than orequal to 65%.

In some embodiments, an anion exchange membrane is provided. The anionexchange membrane comprises a silica-based ceramic comprising Si in anamount greater than or equal to 6 wt % of the silica-based ceramic. Theanion exchange membrane has a chloride ion conductivity of greater thanor equal to 0.00001 S/cm.

In some embodiments, the anion exchange membrane has a silica-basedceramic and a chloride ion conductivity of greater than or equal to0.00001 S/cm and a linear expansion of less than or equal to 10%.

In some embodiments, an anion exchange membrane is provided. The anionexchange membrane comprises a silica-based ceramic comprising Si in anamount greater than or equal to 6 wt % of the silica-based ceramic. Theanion exchange membrane has an osmotic water permeance of less than orequal to 100 mL/(hr·bar·m²).

In some embodiments, the anion exchange membrane comprises asilica-based ceramic comprising Si in an amount greater than or equal to6 wt % of the silica-based ceramic. The silica-based ceramic comprisespores, wherein an average diameter of the pores of the silica-basedceramic is larger when the anion exchange membrane is in a hydratedstate than when the anion exchange membrane is in a dry state by afactor of greater than or equal to 1.1.

In some embodiments, the anion exchange membrane comprises asilica-based ceramic comprising Si in an amount greater than or equal to6 wt % of the silica-based ceramic. When the anion exchange membrane isin a dry state, the pores of the silica-based ceramic fit a model ofsmall angle scattering spectra with intensity (I) as a function of ascattering vector, q, as follows:

${{I(q)} = {\frac{1}{a + {c_{1}q^{2}} + {c_{2}q^{4}}} + {bck}}},$

wherein a, c₁, and c₂ are adjustable parameters and bck is backgroundscattering; and when the anion exchange membrane is in a hydrated statethe pores of the silica-based ceramic fit a core-shell model of smallangle scattering spectra with intensity (I) as a function of ascattering vector, q, as follows:

$\mspace{79mu} {{{I(q)} = {{{P(q)}{S(q)}} + {b{ck}}}},\mspace{79mu} {{S(q)} = {1 + {\frac{D_{f}{\Gamma \left( {D_{f} - 1} \right)}}{\left. \left\lbrack {1 + {{1/q}\; \xi}} \right)^{2} \right\rbrack^{{({D_{f} - 1})}/2}}\frac{\sin \left\lbrack {\left( {D_{f} - 1} \right){\tan^{- 1}\left( {q\xi} \right)}} \right\rbrack}{\left( {qR_{0}} \right)^{D_{f}}}}}},{{P(q)} = {{\frac{scale}{V_{s}}\left\lbrack {{3{V_{c}\left( {\rho_{c} - \rho_{s}} \right)}\frac{\left\lbrack {{\sin \left( {qr}_{c} \right)} - {{qr}_{c}{\cos \left( {qr}_{c} \right)}}} \right\rbrack}{\left( {qr}_{c} \right)^{3}}} + \mspace{256mu} {3{V_{s}\left( {\rho_{s} - \rho_{block}} \right)}\frac{\left\lbrack {{\sin \left( {qr}_{s} \right)} - {{qr}\; \cos \; \left( {qr}_{s} \right)}} \right\rbrack}{\left( {qr}_{s} \right)^{3}}}} \right\rbrack}^{2} + {bck}}},}$

wherein R_(o) is a radius of the building blocks (pores), ρ_(solvent) isa scattering length density of the silica-based ceramic, D_(f) is afractal dimension, ξ is a correlation length, Γ is the standardmathematical gamma function, scale is a volume fraction of buildingblocks of the measured silica-based ceramic, V_(c) is a volume of thecore, V_(s) is a volume of the shell, ρ_(c) is a scattering lengthdensity of the core, ρ_(s) is a scattering length density of the shell,ρ_(block) is a scattering length density of the pores, r_(c) is a radiusof the core, r_(s) is a radius of the shell, and bck is backgroundscattering.

In some embodiments, a method of forming an anion exchange membrane isdescribed. In some embodiments, the method comprises exposing a poroussupport membrane, at least a portion of which is coated with asilica-based ceramic, to an amine, The silica-based ceramic comprises amoiety comprising a leaving group covalently bound to the silica-basedceramic. The silica-based ceramic comprises Si in an amount greater thanor equal to 6 wt % of the silica-based ceramic. The method comprisesreacting the amine with the moiety to release the leaving group and forma quaternary ammonium group covalently bound to the silica-basedceramic.

In some embodiments, a method of forming an anion exchange material isdescribed. In some embodiments, the method comprises exposing a resincomprising a silica-based ceramic, to an amine. The silica-based ceramiccomprises a moiety comprising a leaving group covalently bound to thesilica-based ceramic. The silica-based ceramic comprises Si in an amountgreater than or equal to 6 wt % of the silica-based ceramic. The methodcomprises reacting the amine with the moiety to release the leavinggroup and form a quaternary ammonium group covalently bound to thesilica-based ceramic.

In some embodiments, a method for using an anion exchange membranedescribed herein in an electrochemical application is provided. Themethod comprises contacting the anion exchange membrane with anelectrolyte. The method comprises passing current through an electrodein electrical communication with the electrolyte.

In some embodiments, a method for using an anion exchange materialdescribed herein in an electrochemical application is provided. Themethod comprises contacting the anion exchange material with anelectrolyte. The method comprises passing current through an electrodein electrical communication with the electrolyte.

In some embodiments, a method for using an anion exchange membranedescribed herein as an adsorbent material is provided. In someembodiments, the method comprises flowing a fluid through the anionexchange membrane. The method comprises adsorbing a component of thefluid.

In some embodiments, a method for using an anion exchange materialdescribed herein as an adsorbent material is provided. The methodcomprises flowing a fluid through the anion exchange material. Themethod comprises adsorbing a component of the fluid.

In some embodiments, a method for using an anion exchange membranedescribed herein in a separation application is provided. The methodcomprises applying a transmembrane pressure to the anion exchangemembrane.

Other advantages and novel features of the present invention will becomeapparent from the following detailed description of various non-limitingembodiments of the invention when considered in conjunction with theaccompanying figures. In cases where the present specification and adocument incorporated by reference include conflicting and/orinconsistent disclosure, the present specification shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present invention will be described byway of example with reference to the accompanying figures, which areschematic and are not intended to be drawn to scale. In the figures,each identical or nearly identical component illustrated is typicallyrepresented by a single numeral. For purposes of clarity, not everycomponent is labeled in every figure, nor is every component of eachembodiment of the invention shown where illustration is not necessary toallow those of ordinary skill in the art to understand the invention. Inthe figures:

FIG. 1A is a schematic cross-sectional illustration of an exemplaryanion exchange membrane comprising a silica-based ceramic, according tosome embodiments;

FIG. 1B is a schematic cross-sectional illustration of an exemplaryanion exchange membrane comprising a silica-based ceramic, and an insetshowing a zoomed in view of pores of the silica-based ceramic, accordingto some embodiments;

FIG. 2A is a schematic top-down illustration of an exemplary anionexchange membrane comprising a silica-based ceramic and a porous supportmembrane, according to some embodiments;

FIG. 2B is a schematic cross-sectional illustration of an exemplarysilica-based ceramic coating on a portion of a porous support membranecomponent, according to some embodiments;

FIG. 3 is a schematic illustration of quaternary ammonium groupscovalently bound to silica-based ceramic, according to some embodiments;

FIG. 4A is a schematic cross-sectional illustration of an exemplarysilica-based ceramic coating on a portion of a porous support membranecomponent, where the coating comprises quaternary ammonium groups thatare substantially homogeneously distributed within the silica-basedceramic across a thickness of the coating, according to someembodiments;

FIG. 4B is a schematic cross-sectional illustration of an exemplarysilica-based ceramic coating on a portion of a porous support membranecomponent, where the coating comprises quaternary ammonium that are notsubstantially homogeneously distributed within the silica-based ceramicacross a thickness of the coating, according to some embodiments;

FIG. 5 is a schematic top-down illustration of an exemplary anionexchange membrane comprising a silica-based ceramic and a compressibleedging material, according to some embodiments;

FIG. 6 is a flow diagram showing steps of an exemplary procedure forfabricating a ceramic anion exchange membrane, according to someembodiments;

FIG. 7 is a schematic cross-sectional illustration of an anion exchangematerial comprising a silica-based ceramic, where the anion exchangematerial comprises quaternary ammonium groups covalently bound to thesilica-based ceramic, according to some embodiments;

FIGS. 8A-8D show anion permselectivity, osmotic water permeance chlorideion conductivity, and small angle X-ray scattering data and fittingresults for exemplary anion exchange membranes, according to someembodiments;

FIG. 9A shows small angle X-ray scattering data and fitting results foran exemplary anion exchange membrane, according to certain embodiments;

FIGS. 9B-9D show pore radius, volumetric porosity, and anion exchangecapacity data for exemplary anion exchange membranes as a function ofTEOS:TMAPS mole ratio, according to some embodiments;

FIGS. 10A-10B show permselectivity and chloride ion conductivity datafor exemplary anion exchange membranes at different porous supportmembrane thicknesses, according to some embodiments;

FIGS. 11A-11B show permselectivity and chloride ion conductivity datafor exemplary anion exchange membranes as a function of number ofcoatings, time exposed to silicon-containing precursor sols, and dryingconditions, according to some embodiments; and

FIG. 11C shows a cross-sectional SEM image of an exemplary anionexchange membrane, according to some embodiments.

DETAILED DESCRIPTION

Anion exchange membranes and materials including silica-based ceramics,and associated methods, are provided. In some aspects, anion exchangemembranes that include a silica-based ceramic that forms a coating onand/or within a porous support membrane are described. The anionexchange membranes and materials may have certain structural or chemicalattributes (e.g., pore size/distribution, chemical functionalization)that, alone or in combination, can result in advantageous performancecharacteristics in any of a variety of applications for which selectivetransport of negatively charged ions through membranes/materials isdesired. For example, the anion exchange membranes or materialsdescribed herein may display relatively high anion exchange capacity,anion permselectivity, and/or mechanical burst strength, while in somecases also undergoing relatively low dimensional swelling (e.g., when incontact with water). In some embodiments, the silica-based ceramiccontains relatively small pores (e.g., substantially sphericalnanopores) that may contribute to some such advantageous properties.

In some embodiments, the anion exchange membrane or material includesquaternary ammonium groups covalently bound to the silica-based ceramic.In some such cases, the quaternary ammonium groups are present inrelatively high loadings compared to certain existing anion exchangematerials. In some embodiments, the quaternary ammonium groups aresubstantially homogeneously distributed within the silica-based ceramicacross a thickness of a coating formed by the silica-based ceramic,which can, in some cases, lead to benefits over certain existingmembranes that may be functionalized only at or near the surface.

In some embodiments, the anion exchange membranes and materialsdescribed herein can be produced via sol-gel techniques, such as via theco-condensation of certain silanes on porous support membranes. Theanion exchange membranes and materials may be useful in a number ofapplications, such as electrochemical (e.g., redox flow battery) andpurification (e.g., desalination, gas/liquid separation) processes.

Certain existing anion exchange membranes that are commerciallyavailable are made from hydrocarbon- or perfluorocarbon-based polymerscontaining covalently bound quaternary ammonium moieties. As a result,these anion exchange membranes have nanostructures characterized by amixture of interconnected worm-like hydrophilic domains in a hydrophobicmatrix. In the presence of water (e.g., when certain existing anionexchange membranes are in use), these hydrophilic domains tend to swell(e.g., undergo dimensional swelling such as linear expansion). Swellingof anion exchange membranes can be problematic in certain applications,because the swelling can cause tensile forces that can lead to tearingof the membrane and device failure. While certain techniques such aschemical cross-linking and/or mechanical reinforcement of the membranecan sometimes reduce swelling, improved compositions and architecturesthat can more effectively reduce swelling while preserving or evenenhancing the performance of anion exchange membranes and materials areneeded.

It has been observed that anion exchange membranes that include rigidstructures such as ceramics can undergo less swelling than hydrocarbon-or perfluorocarbon-based membranes. However, certain existing ceramicshave been considered too brittle to be used in standalone ceramic-basedmembranes. Therefore, previous attempts at introducing ceramics intoanion exchange membranes have typically involved incorporation ofceramic nanoparticles into, for example, polymer matrices. In thecontext of the present disclosure, it has been unexpectedly observedthat it is possible to achieve anion exchange membranes and materialsthat include silica-based ceramics without needing to resort to usingnanoparticles incorporated into polymeric matrices. For example, it hasbeen observed that anion exchange membranes containing silica-basedceramics comprising functional groups such as quaternary ammonium groupthat are covalently bound to the silica-based ceramic are achievable. Insome embodiments, such functionalized silica-based ceramic compositionscan have ordered, nanoporous structures. In some embodiments, theresulting anion exchange membranes display unexpectedly beneficialperformance characteristics (e.g., relatively high anion exchangecapacity, relatively high chloride ion conductivity, relatively highpermselectivity, high mechanical burst strength), while displayingrelatively low dimensional swelling. Such anion exchange membranes andmaterials, and methods for making and using them, are described herein.

In one aspect, anion exchange membranes are generally described. FIG. 1Ais a schematic cross-sectional illustration of an exemplary anionexchange membrane 100. In some embodiments, the anion exchange membranecan realize any of a variety of advantageous properties and performancecharacteristics reported in the present disclosure. For example, anionexchange membrane 100 may display a relatively high anion exchangecapacity, relatively high anion permselectivity, relatively highchloride ion conductivity, relatively low osmotic water permeance,and/or relatively low dimensional swelling (e.g., relatively low linearexpansion), the details of which are provided in greater detail below.As mentioned above, the anion exchange membrane may be suitable for usein any of a variety of applications, described in more detail below.

Referring again to FIG. 1A, exemplary anion exchange membrane 100comprises silica-based ceramic 150. In some embodiments, thesilica-based ceramic is a ceramic comprising or formed of a network ofsilica (SiO₂), though the silica-based ceramic can include groups (e.g.,terminal moieties) not encompassed by the SiO₂ formula. In someembodiments, the silica-based ceramic is porous (e.g., nanoporous). FIG.1B is a schematic cross-sectional illustration of an exemplary anionexchange membrane 100 comprising an exemplary silica-based ceramic 150that is porous (e.g., nanoporous), according to some embodiments. FIG.1B shows an inset depicting a zoomed-in view of silica-based ceramic 150showing exemplary pores, including an exemplary pore 152. The porosity(e.g., nanoporosity) of the silica-based ceramic may contribute, atleast in part, to the performance characteristics of the anion exchangemembrane. The silica-based ceramic is described in more detail below. Itshould be understood that the figures shown herein are for illustrativepurposes, and may not necessarily be drawn to scale.

In some embodiments, the anion exchange membrane comprises a poroussupport membrane. For example, in some embodiments, anion exchangemembrane 100 comprises a porous support membrane. The porous supportmembrane may provide for mechanical support for the overall anionexchange membrane. FIG. 2A shows a schematic top-down illustration of anexemplary anion exchange membrane 100 comprising a silica-based ceramic150 and a porous support membrane 130 hidden by silica-based ceramic150, according to some embodiments. For illustrative purposes, FIG. 2Ashows porous support membrane 130 without a silica-based ceramic 150present to the left of the arrow, while anion exchange membrane 100 tothe right side of the arrow includes silica-based ceramic 150 present,which hides porous support membrane from view. It should be understoodthat FIG. 2A is illustrative for a non-limiting embodiment, and in someembodiments, the coating formed by the silica-based ceramic does notcompletely cover the porous support membrane. For example, in some suchembodiments, portions of porous support membrane 130 may not be hiddenby silica-based ceramic 150.

In some embodiments, the anion exchange membrane comprises asilica-based ceramic that coats at least a portion of the porous supportmembrane. Referring again to FIG. 2A, anion exchange membrane 100comprises silica-based ceramic 150, which coats porous support membrane130 (hidden from view in anion exchange membrane 100 to the right of thearrow). In some such embodiments, the silica-based ceramic forms acoating on and/or within the porous support membrane. For example, theporous support membrane may be impregnated or encapsulated in thesilica-based ceramic. In some embodiments, the silica-based ceramiccoats a portion, but not all, of the porous support membrane. In suchembodiments, the porous support membrane may be substantially coatedwith the silica-based ceramic.

FIG. 2B shows a schematic cross-sectional view of an exemplary coating140 formed by silica-based ceramic 150, according to some embodiments.As shown illustratively in this figure, coating 140 of silica-basedceramic 150 is on a surface of porous support membrane component 135(e.g., a single fiber on or within a porous support membrane), across-section of which is shown in FIG. 2B, in accordance with someembodiments. This exemplary embodiment (e.g., a coated fiber) may be apart of a anion exchange membrane in which a silica-based ceramic coatsthe porous support membrane completely, or coats a porous supportmembrane partially.

It should be understood that when a portion (e.g., layer, coating,) is“on”, “adjacent”, “in contact with”, or “supported by” another portion,it can be directly on the portion, or an intervening portion (e.g.,layer, coating) also may be present. A portion that is “directly on”,“directly adjacent”, “in direct contact with”, or “directly supportedby” another portion means that no intervening portion is present. Itshould also be understood that when a portion is referred to as being“on”, “adjacent”, “in contact with”, or “supported by” another portion,it may cover the entire portion or a part of the portion.

In some embodiments, the coating of the silica-based ceramic (e.g.,coating 140) is present on (e.g., directly on) the surface of the poroussupport membrane. In some embodiments, the coating is present on thesurface of the porous support membrane while the interior of the poroussupport membrane is not substantially coated. However, in otherembodiments, the coating of the silica-based ceramic is present withinat least a portion of the interior of the porous support membrane (i.e.,through the thickness of the porous support membrane). As one example,the coating of the silica-based ceramic is formed on components in theinterior of the porous support membrane accessible via, for example,pores or voids. In some such cases, the coating fills at least a portionor all of the pores of the porous support membrane. In some embodiments,at least a portion of the interior of the porous support membrane iscoated, while the surface of the porous support membrane is notsubstantially coated.

As described in more detail below, the porous support membrane mayinclude support components such as fibers that provide structuralsupport to the membrane. In some embodiments, substantially all of thesupport components of the porous support membrane are coated with thesilica-based ceramic. As one example, in some embodiments, the poroussupport membrane comprises a non-woven fabric of fibers. In some suchcases, substantially all of the fibers, including fibers in the interiorof the porous support membrane, are coated with the silica-basedceramic. However, in other embodiments, not all of the supportcomponents of the porous support membrane are coated with thesilica-based ceramic. For example, in some embodiments in which theporous support membrane comprises fibers as support components, not allfibers are coated with a silica-based ceramic. The extent of the coatingmay vary. In some cases, the coating of the silica-based ceramic coversthe entire porous support membrane (e.g., as shown with anion exchangemembrane 100 to the right of the arrow in FIG. 2A), though in othercases, the coating of the silica-based ceramic covers only a portion ofthe porous support membrane (e.g., only a subset of the area of theporous support membrane is coated, or only a portion of the supportcomponents are coated).

In some embodiments in which the silica-based ceramic forms a coating onand/or within the porous support membrane, the silica-based ceramicfills substantially all of the pores of the porous support membrane. Forexample, referring again to FIG. 2A, in some embodiments, when thesilica-based ceramic coats porous support membrane 130, all of the poresof porous support membrane 130, including pore 132, are completelyfilled by the silica-based ceramic. In such embodiments, the porosity ofthe resulting overall anion exchange membrane would correspond to theporosity of the silica-based ceramic material. In other embodiments inwhich the silica-based ceramic forms a coating on and/or within theporous support membrane, the silica-based ceramic does not completelyfill the pores of the porous support membrane, but reduces the pore size(e.g., average pore diameter) of the porous support membrane. In suchembodiments, the overall porosity of the resulting overall anionexchange membrane would be different than the porosity of thesilica-based ceramic material itself. The resulting overall exchangemembrane in this case will have a porosity that is different than theporosity of the silica-based ceramic coating because both thereduced-in-size pores of the porous support membrane and the porescorresponding to the silica-based ceramic will be present. In suchembodiments, the silica-based ceramic coating may have a porosity in oneor more of the ranges described herein, and the overall anion exchangemembrane may have a porosity in one or more of the ranges describedherein.

In some, but not necessarily all embodiments, the anion exchangemembrane comprises one or more additional layers or coatings on thecoating comprising the silica-based ceramic (e.g., on top of thesilica-based ceramic coating). However, in some embodiments, no otherlayers or coatings are present on the coating comprising thesilica-based ceramic (e.g., the silica-based coating forms theouter-most surface of the anion exchange membrane). In some embodiments,the silica-based ceramic forms a single layer on the porous supportmembrane.

The formation of a coating of the silica-based ceramic on and/or withinat least a portion of the porous support membrane can be accomplishedusing any of a variety of suitable techniques. In some embodiments, thecoating of the silica-based ceramic (e.g., coating 140) is formed usingsol-gel techniques. For example, referring back to FIG. 2A, in someembodiments, porous support membrane 130 (shown to the left of thearrow) is coated using sol-gel techniques, thereby resulting in anionexchange membrane 100 comprising a silica-based ceramic 150 coated onand/or within at least a portion of porous support membrane 130 (shownto the right of the arrow). In some cases, sol-gel techniques such asthose described herein can provide for a relatively rapid andinexpensive formation of anion exchange membranes comprisingsilica-based ceramics. In some such cases, relatively mild conditionscan be used to form the coating of the silica-based ceramic usingsol-gel techniques, and the resulting silica-based ceramics may possesscertain structural properties (e.g., ordered nanopores) that can in somecases provide for advantageous performance. Exemplary sol-gel techniquesare described in more detail below.

In some embodiments, the silica-based ceramic comprises one or morefunctional groups covalently bound to the silica-based ceramic. Thepresence of functional groups covalently bound to the silica-basedceramic may contribute at least in part to the performance of the anionexchange membrane. For example, in some embodiments, the silica-basedceramic comprises functional groups capable of associating anddisassociating cations. In some embodiments, the functional groupscovalently bound to the silica-based ceramic are positively-chargedfunctional groups. For example, in some embodiments, the functionalgroups covalently bound to the silica-based ceramic are quaternaryammonium groups. In some embodiments, the functional groups covalentlybound to the silica-based ceramic are imidazole groups. In someembodiments, the functional groups covalently bound to the silica-basedceramic are weak base groups such as amine groups (e.g., tertiary aminegroups). The functional groups may be bound to Si in the silica-basedceramic via a linking group (e.g., an organic linking group). Forexample, the nitrogen of the quaternary ammonium groups may becovalently bound to Si in the silica-based ceramic via an organic linkersuch as a linker chosen from optionally-substituted C₁₋₁₈ alkylene andarylene (or C₁₋₈ alkylene and arylene, or C₁₋₄ alkylene and arylene). Itshould be understood that in the present disclosure, any description ofan item being “chosen from” a list of items can be replaced with adescription of an item being selected from a “group consisting of” thoseitems. For example, in some embodiments, the nitrogen of the quaternaryammonium groups may be covalently bound to Si in the silica-basedceramic via an organic linker such as a linker selected from the groupconsisting of optionally-substituted C₁₋₁₈ alkylene and arylene.

The functional group may be able to associate and dissociate cationssuch as protons or certain metal ions. As an example, quaternaryammonium groups bound to the silica-based ceramic may be able toassociate and disassociate anions such as hydroxide or halides.Exemplary anions that may be able to associate and dissociate with thefunctional groups (e.g., quaternary ammonium groups) include F⁻, Cl⁻,Br⁻, I⁻, OH⁻, SO₃ ⁻, CO₃ ⁻, PO₄ ³⁻, BO₃ ⁻, NO₃ ⁻, NO₂ ⁻, and ClO₃ ⁻.

FIG. 3 is a schematic illustration of quaternary ammonium groupscovalently bound to a silica-based ceramic 150, according to someembodiments. As shown illustratively in this figure, the quaternaryammonium groups are covalently attached to the interior portions of thesilica-based ceramic material. In some embodiments, the functionalgroups (e.g., quaternary ammonium groups) are exposed at an exteriorsurface of the silica-based ceramic (e.g., the exterior of a coating ofthe silica-based ceramic). In some cases, the functional groupscovalently bound to the silica-based ceramic groups (e.g., quaternaryammonium groups) are exposed at surfaces of pores in the silica-basedceramic. For example, in FIG. 3, quaternary ammonium groups covalentlybound to silica-based ceramic 150 are shown exposed at a surface of apore 152 of the silica-based ceramic. Having functional groups such asquaternary ammonium groups present at the surface of pores of thesilica-based ceramic may, in some embodiments, allow for relativelyefficient transport of anions through the anion exchange membrane,and/or relatively high anion exchange capacity for the anion exchangemembrane.

One of ordinary skill in the art would understand that the relativeamount of the conjugate acid of a functional group covalently bound tothe silica-based ceramic compared to the amount of conjugate base of thefunctional group present at any given time will depend on the conditionsand environment of the anion exchange membrane or material. For example,in embodiments where the functional group is an imidazole or an amine(e.g., a tertiary amine), the relative number of imidazolium vs.imidazole or ammonium vs. amine groups will depend at least in part onthe pH of any solution with which the membrane or material is incontact, the pK_(a) of other functional groups if present, and/or theconcentration of anions in any solution for which the membrane ormaterial is in contact.

In some embodiments, the silica-based ceramic comprises quaternaryammonium groups covalently bound to silica-based ceramic, and thequaternary ammonium groups are substantially homogeneously distributedwithin the silica-based ceramic across a thickness of the coating. Athickness of the coating refers to a thickness in a direction going froma surface of the component of the porous support membrane coated by thecoating (e.g., the surface of a single fiber of the porous supportmembrane) to the closest exposed surface of the silica-based ceramiccoating. An exposed surface of the silica-based ceramic coating refersto any surface of the silica-based ceramic that interfaces with theexterior of the anion exchange membrane, another layer or domain ofmaterial, or an unfilled pore or void of the porous support membrane.For example, in one embodiment, an exposed surface may be exposed to airor another environment different from the silica-based ceramic coatingitself. FIG. 4A is a schematic cross-sectional illustration of anexemplary coating 140 of a silica-based ceramic 150 on a portion of aporous support membrane component 135 (e.g., a fiber on or within aporous support membrane), according to some embodiments. In someembodiments, coating 140 in FIG. 4A comprises quaternary ammonium groupsthat are substantially homogeneously distributed within silica-basedceramic 150 across a thickness 160 of coating 140. Having functionalgroups such as quaternary ammonium groups substantially homogeneouslydistributed within the silica-based ceramic across a thickness of thecoating may, in some cases, result in a number of advantages. Oneadvantage may be that a substantially homogeneous distribution offunctional groups in the silica-based ceramic can allow for a relativelyhigh loading of the functional groups for a given amount of silica-basedceramic, which can lead to high anion exchange capacities per unit mass,and beneficial performance characteristics. Another possible advantageis that a substantially homogeneous distribution of functional groups inthe silica-based ceramic can result in relatively small distancesbetween functional groups within the membrane, as opposed to certainexisting membranes where functional groups (e.g., quaternary ammoniumgroups) are relatively localized (e.g., near a surface), which canresult in regions of the membrane having a relatively low amount of thefunctional groups and can limit anion conductivity. A substantiallyhomogeneous distribution of functional groups (e.g., quaternary ammoniumgroups) can be achieved, for example, using certain sol-gel techniques,as described in more detail below.

FIG. 4B is a schematic cross-sectional illustration of an exemplarycoating 240 comprising a silica-based ceramic 250 on a portion of aporous support membrane component 135 (e.g., a fiber on or within aporous support membrane), according to some embodiments. In FIG. 4B,coating 240 comprises quaternary ammonium groups that are notsubstantially homogeneously distributed within silica-based ceramic 250across a thickness 260 of coating 240. Rather, in FIG. 4B, thequaternary ammonium groups are localized at or near the surface ofcoating 240, leaving a region 245 of the coating without quaternaryammonium groups.

Such a distribution of quaternary ammonium groups that is notsubstantially homogeneously distributed may result from coatingtechniques that use surface functionalization, rather than the certainsol-gel techniques described herein. For example, a coating comprising asilica-based ceramic comprising quaternary ammonium groups that are notsubstantially homogeneously distributed may result from fabricationtechniques where a support (e.g., porous support membrane) is firstcoated with a material (e.g., with a ceramic such as a silica-basedceramic) that does not comprise quaternary ammonium groups (or arelatively low amount of quaternary ammonium groups). Then, followingthe first coating step, a second coating step is performed where amaterial that does comprise quaternary ammonium groups (or comprises arelatively higher amount of quaternary ammonium groups) is coated on thefirst coating. Having a silica-based ceramic coating that does not havea substantially homogeneous distribution of quaternary ammonium groupsmay result in relatively poor performance of the resulting anionexchange membrane. For example, in some embodiments, the anion exchangemembranes may have a relatively lower loading of quaternary ammoniumgroups compared to anion exchange membranes having coatings that have asubstantially homogeneous distribution of quaternary ammonium groups.Additionally, in some cases, such coatings that do not have asubstantially homogeneous distribution of quaternary ammonium groups andconsequently have regions having a relatively low abundance ofquaternary ammonium groups (e.g., region 245) may have relatively loweranion conductivity due to such regions.

In some embodiments in which the quaternary ammonium groups aresubstantially homogeneously distributed within the silica-based ceramicacross a thickness of the coating, the amount of quaternary ammoniumgroups does not vary by more than 50% at any given point within across-section of thickness of the coating compared to an average amountof the quaternary ammonium groups in the silica-based ceramic. Forexample, referring again to FIG. 4A, the amount of quaternary ammoniumgroups at an arbitrary point A, or at an arbitrary point B, ofcross-section 143 of coating 140 does not vary by more than 50% comparedto the average amount of quaternary ammonium groups in coating 140. Insome embodiments in which the quaternary ammonium groups aresubstantially homogeneously distributed within the silica-based ceramicacross a thickness of the coating, the amount of quaternary ammoniumgroups is distributed within the silica-based ceramic such that anygiven point within a cross-section of thickness of the coating is withingreater than or equal to 50%, greater than or equal to 60%, greater thanor equal to 70%, greater than or equal to 75%, greater than or equal to80%, greater than or equal to 90%, greater than equal to 95%, or greaterthan or equal to 99% of the average amount of quaternary ammonium groupsin the coating. In some embodiments, the amount of quaternary ammoniumgroups is distributed within the silica-based ceramic such that anygiven point within a cross-section of thickness of the coating is withinless than or equal to 100%, less than or equal to 99%, less than orequal to 95%, less than or equal to 90%, less than or equal to 75%, lessthan or equal to 70%, less than or equal to 60%, or less of the averageamount of quaternary ammonium groups within the coating. Combinations ofthese ranges are possible. For example, in some embodiments, the amountof quaternary ammonium groups is distributed within the silica-basedceramic such that any given point within a cross-section of thickness ofthe coating is within greater than or equal to 50% and less than orequal to 100% of the total average amount of quaternary ammonium groupswithin the coating. As an exemplary calculation, if a silica-basedceramic were determined to have an average amount of quaternary ammoniumgroups of 5 weight percent (wt %) (as determined by scanning electronmicroscopy/energy-dispersive X-ray techniques (SEM/EDX)), and all pointswithin at least 5 cross-sections across the thickness of thesilica-based ceramic (e.g., point A in FIG. 4A) are determined to havean amount of quaternary ammonium groups of greater than or equal to 2.5wt % and less than or equal to 7.5 wt %, then that silica-based ceramicwould be considered to have quaternary ammonium groups substantiallyhomogeneously distributed across a thickness of the coating based on theaverage amount of quaternary ammonium groups measured.

In contrast, in some cases in which the quaternary ammonium groups arenot substantially homogeneously distributed within the silica-basedceramic across a thickness of the coating, the amount of quaternaryammonium groups are within less than 50% of the average amount ofquaternary ammonium groups within the coating (in other words, theamount of quaternary ammonium groups varies by more than 50% at anygiven point within a cross-section of thickness of the coating comparedto an average total amount of the quaternary ammonium groups in thesilica-based ceramic). For example, referring again to FIG. 4B, theamount of quaternary ammonium groups at an arbitrary point C, or at anarbitrary point D, of cross-section 243 of coating 240 varies by morethan 50% compared to the average amount of quaternary ammonium groups incoating 240. As an exemplary calculation, if a silica-based ceramic weredetermined to have an average amount of quaternary ammonium groups of 5wt %, and any point within a cross-section across the thickness of thesilica-based ceramic (e.g., point D in FIG. 4B) were determined to havean amount of quaternary ammonium groups of less than 2.5 wt % or greaterthan 7.5 wt %, then that silica-based ceramic would not be considered tohave quaternary ammonium groups substantially homogeneously distributedacross a thickness of the coating based on the average amount ofquaternary ammonium groups measured.

In some embodiments in which the quaternary ammonium groups aresubstantially homogeneously distributed within the silica-based ceramicacross a thickness of the coating, the amount of quaternary ammoniumgroups does not vary by more than 75% at any given point within across-section of thickness of the coating compared to a maximum amountof the quaternary ammonium groups in the silica-based ceramic. Forexample, referring again to FIG. 4A, the amount of quaternary ammoniumgroups at an arbitrary point A, or at an arbitrary point B, ofcross-section 143 of coating 140 does not vary by more than 75% comparedto the maximum amount of quaternary ammonium groups in coating 140. Insome embodiments in which the quaternary ammonium groups aresubstantially homogeneously distributed within the silica-based ceramicacross a thickness of the coating, the amount of quaternary ammoniumgroups is distributed within the silica-based ceramic such that anygiven point within a cross-section of thickness of the coating isgreater than or equal to 25%, greater than or equal to 40%, greater thanor equal to 50% greater than or equal to 60%, greater than or equal to70%, greater than or equal to 75%, greater than or equal to 80%, greaterthan or equal to 90%, greater than equal to 95%, or greater than orequal to 99% of the maximum amount of quaternary ammonium groups in thecoating. In some embodiments, the amount of quaternary ammonium groupsis distributed within the silica-based ceramic such that any given pointwithin a cross-section of thickness of the coating is less than or equalto 100%, less than or equal to 99%, less than or equal to 95%, less thanor equal to 90%, less than or equal to 75%, less than or equal to 70%,less than or equal to 60%, or less of the maximum amount of quaternaryammonium groups within the coating. Combinations of these ranges arepossible. For example, in some embodiments, the amount of quaternaryammonium groups is distributed within the silica-based ceramic such thatany given point within a cross-section of thickness of the coating isgreater than or equal to 25% and less than or equal to 100% of the totalmaximum amount of quaternary ammonium groups within the coating. As anexemplary calculation, if a silica-based ceramic were determined to havea maximum amount of quaternary ammonium groups of 10 wt % (as determinedby scanning electron microscopy/energy-dispersive X-ray techniques(SEM/EDX)), and all points within at least 5 cross-sections across thethickness of the silica-based ceramic (e.g., point A in FIG. 4A) aredetermined to have an amount of quaternary ammonium groups of greaterthan or equal to 2.5 wt %, then that silica-based ceramic would beconsidered to have quaternary ammonium groups substantiallyhomogeneously distributed across a thickness of the coating based on themaximum amount of quaternary ammonium groups measured. It should beunderstood that it is the relative amounts of quaternary ammonium groupsthat is important in the above calculation, and the units used toexpress the amounts measured from the SEM/EDX technique are notparticularly important. While weight percent is used in the aboveexemplary calculation, other units for expressing the amount ofquaternary ammonium groups are readily obtainable from the SEM/EDXtechnique or can be derived from the weight percentage as well.

In contrast, in some cases in which the quaternary ammonium groups arenot substantially homogeneously distributed within the silica-basedceramic across a thickness of the coating, the amount of quaternaryammonium groups at a point are less than 25% of the maximum amount ofquaternary ammonium groups within the coating (in other words, theamount of quaternary ammonium groups varies by more than 75% at anygiven point within a cross-section of thickness of the coating comparedto a maximum total amount of the quaternary ammonium groups in thesilica-based ceramic). For example, referring again to FIG. 4B, theamount of quaternary ammonium groups at an arbitrary point C, or at anarbitrary point D, of cross-section 243 of coating 240 varies by morethan 75% compared to the maximum amount of quaternary ammonium groups incoating 240. As an exemplary calculation, if a silica-based ceramic weredetermined to have a maximum amount of quaternary ammonium groups of 10wt %, and any point within a cross-section across the thickness of thesilica-based ceramic (e.g., point D in FIG. 4B) were determined to havean amount of quaternary ammonium groups of less than 2.5 wt %, then thatsilica-based ceramic would not be considered to have quaternary ammoniumgroups substantially homogeneously distributed across a thickness of thecoating based on the maximum amount of quaternary ammonium groupsmeasured.

The amount of quaternary ammonium groups within the coating and withinan arbitrary cross-section of the coating may be determined using acombination of scanning electron microscopy (SEM) and energy-dispersiveX-ray (EDX) techniques. For example, the following procedure can beperformed. The anion exchange membrane is dried and a cross sectionalsample is mounted on to an SEM stub. The sample is first imaged usingsecondary electron and/or backscatter detection, followed by imaging viaEDX. The EDX data can be acquired as a line profile across the crosssectional sample or as a map of the whole sample. The EDX data can thenbe interpreted to determine the average amount or maximum amount (e.g.,in wt %) of quaternary ammonium groups are present in the coating, aswell as amounts of quaternary ammonium groups at points along arbitrarycross-sections using the line profiles from the SEM/EDX data. Three ormore line profiles can be acquired to determine a statisticallyrepresentative set of data.

In some embodiments, quaternary ammonium groups are directly adjacent toa surface of the porous support membrane. For example, referring againto FIG. 4A, coating 140 comprising silica-based ceramic 150 comprisesquaternary ammonium groups, and the quaternary ammonium groups aredirectly adjacent to porous support membrane component 135, therebymaking it directly adjacent to the porous support membrane to whichporous support membrane component 135 belongs, according to someembodiments. In some embodiments, no intervening layer is presentbetween the silica-based ceramic comprising quaternary ammonium groupsin the porous support membrane. For example, in some embodiments, thereis no intervening layer between silica-based ceramic 150 and poroussupport membrane component 135 in FIG. 4A.

In some embodiments, the quaternary ammonium groups are relatively closeto a surface of the porous support membrane (e.g., the surface of thesupport components that make up the porous support membrane). Forexample, in some embodiments, at least some of the quaternary ammoniumgroups are within 1 μm, within 500 nm, within 100 nm, within 50 nm,within 10 nm, within 5 nm, within 1 nm, or less of a surface of theporous support membrane. In some embodiments, at least some of thequaternary ammonium groups are within 1-10 μm of a surface of the poroussupport membrane. In some embodiments, the quaternary ammonium groupsare in contact (e.g., direct contact) with the surface of the poroussupport membrane. The distance between the porous support membrane and aquaternary ammonium group can be determined, for example, using ananalytical electron microscope equipped with a transmission electronmicroscope (TEM) and an X-ray spectrometer.

As mentioned above, in some embodiments, the anion exchange membrane ormaterial has a relatively high loading of functional groups. Forexample, in some embodiments, the anion exchange membrane or materialhas a relatively high loading of quaternary ammonium groups. Having arelatively high loading of functional group such as quaternary ammoniumgroups may at least in part to lead to beneficial performancecharacteristics of the anion exchange membrane or material. For example,a high loading of quaternary ammonium groups may contribute to arelatively high anion exchange capacity, anion permselectivity, and/oranion conductivity (e.g., chloride ion conductivity, hydroxideconductivity). Certain methods described herein, such as certain sol-geltechniques involving co-condensation of functionalized andnon-functionalized silanes, may provide loadings of quaternary ammoniumgroups that are otherwise challenging to achieve using certain existingtechniques.

In some embodiments, quaternary ammonium groups are present in the anionexchange membrane or material in an amount of greater than or equal to0.01 mmol, greater than or equal to 0.05 mmol, greater than or equal 0.1mmol, greater than or equal to 0.3 mmol, greater than or equal to 0.5mmol, greater than or equal to 0.7 mmol, greater than or equal to 1mmol, greater than or equal to 2 mmol, greater than or equal to 3 mmolor more per gram of the anion exchange membrane or material. In someembodiments, quaternary ammonium groups are present in the anionexchange membrane or material in an amount of less than or equal to 10mmol, less than or equal to 5 mmol, or less per gram of the anionexchange membrane or material. Combinations of these ranges arepossible. For example, in some embodiments, quaternary ammonium groupsare present in the anion exchange membrane or material in an amount ofgreater than or equal to 0.01 mmol in less than or equal to 10 mmol, orgreater than or equal to 0.1 mmol and less than or equal to 10 mmol pergram of the anion exchange membrane or material. It should be understoodthat the loadings described herein refer to the total sum of quaternaryammonium cations (i.e., a charged group) and quaternary ammonium salts(i.e., neutral groups comprising quaternary ammonium groups associatedwith anions). For example, if the anion exchange membrane or materialincluded 0.1 mmol of free quaternary ammonium cations and 0.3 mmol ofquaternary ammonium groups associated with anions per gram of the anionexchange membrane or material, the quaternary ammonium groups would bepresent in the anion exchange membrane or material in an amount of 0.4mmol per gram of the anion exchange membrane or material. The loading ofquaternary ammonium groups within the anion exchange membrane ormaterial can be determined by performing the measurement of the anionexchange capacity of the anion exchange membrane as described below, andtaking the number of chloride ions measured in solution (as determinedby the titration) as being equal to the number of quaternary ammoniumgroups in the anion exchange membrane. The loading can then bedetermined using that number of quaternary ammonium groups (in mmol) anddividing by the weight of the dried anion exchange membrane (in g). Itshould be understood that the above quantities and measurements for theloading of quaternary ammonium groups refers to accessible quaternaryammonium groups, and not to quaternary ammonium groups that areinaccessible to solvent and ions (e.g., quaternary ammonium groupstrapped in enclosed pores that cannot be contacted by solvent oranions).

As described above, the silica-based ceramic (e.g., the silica-basedceramic 150), may be a ceramic comprising predominantly a network ofsilica (SiO₂), though the silica-based ceramic can include groups (e.g.,terminal moieties) not described by the SiO₂ formula. For example, insome embodiments, the silica-based ceramic comprises a network a silicacomprising terminal hydroxy groups, terminal organic groups, and/orterminal functional groups (e.g., quaternary ammonium groups). In someembodiments, a relatively high percentage of the Si atoms in thesilica-based ceramic are in a tetrahedral environment and are bound toeither an oxygen, a hydroxy group, or a functional group (e.g.,quaternary ammonium group. For example, in some embodiments, a relativehigh percentage of the silica-based ceramic can be described using thefollowing structure (I):

wherein each R group can independently be hydroxy, —OSiR₃, or a moietycontaining a functional group such as a quaternary ammonium group. Forexample, in some cases, R can be an trialkylammoniumalkane acid groupsuch as N,N,N-trimethylammoniumpropane. As can be seen from thisstructure, the silica-based ceramic can contain an extended (though notnecessarily single-crystalline) ceramic structure comprising functionalgroups such as quaternary ammonium groups covalently bound to thesilica-based ceramic. For example, in some embodiments, the silica-basedceramic can contain an extended ceramic structure that can be describedusing the following structure (II):

wherein each R group can independently be hydroxy, —OSiR₃, or a moietycontaining a functional group such as a quaternary ammonium group.

In some embodiments, the silica-based ceramic can contain a structurethat can be described using the following structure (III):

wherein each R group can independently be hydroxy, —OSiR₃, or a moietycontaining a functional group such as a quaternary ammonium group, andR′ can independently be optionally-substituted alkyl, cyclyl, or aryl.

The silica-based ceramic of the anion exchange membrane may have one ormore properties of ceramics known in the art. For example, thesilica-based ceramic may be relatively brittle, have a relatively highdensity, have a relatively high hardness, and/or have a relatively highmelting point. In some embodiments, the silica-based ceramic ispolycrystalline. The silica-based ceramic described herein stands incontrast to anion exchange membranes comprising particles (e.g.,nanoparticles) of silica (e.g., functionalized silica nanoparticles)suspended in a non-silica-based matrix (e.g., a polymer matrix such as acarbon-based polymer matrix).

In some embodiments, Si is present in a relatively high amount in thesilica-based ceramic. Si may be present in a relatively high amount inthe silica-based ceramic due to the silica-based ceramic beingpredominantly silica-based, rather than having a relatively highpercentage of other components, such as a polymer matrix. In someembodiments, the silica-based ceramic comprises Si in an amount ofgreater than or equal to 6 weight percent (wt %), greater than or equalto 10 wt %, greater than equal to 12 wt %, greater than or equal to 15wt %, greater than or equal to 17 wt %, greater than or equal to 20 wt%, greater than or equal to 24 wt %, greater than or equal to 30 wt %,greater than or equal to 40 wt %, or more in the silica-based ceramic.In some embodiments, the silica-based ceramic comprises Si in an amountless than or equal to 60 wt %, less than or equal to 50 wt %, less thanor equal to 47 wt %, less than or equal to 40 wt %, less than or equalto 30 wt %, less than or equal to 28 wt %, less than or equal to 26 wt%, less than or equal to 24 wt %, less than or equal to 22 wt %, lessthan or equal to 20 wt %, less than or equal to 17 wt %, or less in thesilica-based ceramic. Combinations of these ranges are possible. Forexample, in some embodiments, the silica-based ceramic comprises Si inan amount greater than or equal to 6 wt % and less than or equal to 60wt %, or greater than or equal to 11 wt % and less than or equal to 26wt % in the silica-based ceramic.

In some embodiments, the silica-based ceramic comprises Si in an amountof greater than or equal to 1.5 mole percent (mol %), greater than orequal to 3 mol %, greater than or equal to 5 mol %, greater than orequal to 8 mol %, greater than or equal to 10 mol %, greater than orequal to 12 mol %, greater than or equal to 15 mol %, greater than orequal to 18 mol %, greater than or equal to 20 mol %, or more in thesilica-based ceramic. In some embodiments, the silica-based ceramiccomprises Si in an amount less than or equal to 33.4 mol %, to 30 mol %,less than or equal to 28 mol %, less than or equal to 26 mol %, lessthan or equal to 24 mol %, less than or equal to 22 mol %, less than orequal to 20 mol %, less than or equal to 18 mol %, or less in thesilica-based ceramic. Combinations of these ranges are possible. Forexample, in some embodiments, the silica-based ceramic comprises Si inan amount greater than or equal to 1.5 mol % and less than or equal to33.4 mol %, greater than or equal to 8 mol % and less than or equal to20 mol %, greater than or equal to 2.8 mol % and less than or equal to18 mol %, or greater than or equal to 12 mol % and less than or equal to18 mol % in the silica-based ceramic.

In some embodiments in which the silica-based ceramic comprises anitrogen-containing functional group such as a quaternary ammoniumgroup, the molar ratio of Si to nitrogen in the silica-based ceramicdepends on the loading of the nitrogen-containing functional groups inthe silica-based ceramic. In some embodiments, the silica-based ceramichas a silicon-to-nitrogen molar ratio of greater than or equal to 1:1,greater than or equal to 1.5:1, greater than or equal to 2:1, greaterthan or equal to 3:1, greater than or equal to 4:1, greater than orequal to 5:1, greater than or equal to 10:1, greater than or equal to25:1, or more. In some embodiments, the silica-based ceramic has asilicon-to-nitrogen molar ratio of less than or equal to 120:1, lessthan or equal to 75:1, less than or equal to 50:1, less than or equal to25:1, less than or equal to 10:1, less than or equal to 4:1, or less.Combinations of these ranges are possible. For example, in someembodiments, the silica-based ceramic has a silicon-to-nitrogen molarratio of greater than or equal to 1:1 and less than or equal to 120:1,greater than or equal to 1:1 and less than or equal to 10:1, or greaterthan or equal to 1:1 and less than or equal to 4:1.

In some embodiments, the molar ratio of Si to carbon in the silica-basedceramic depends on the loading of carbon containing groups within thesilica-based ceramic, such as organic moieties (e.g., organic functionalgroups). In some embodiments, the silica-based ceramic has asilicon-to-carbon (Si:C) molar ratio of greater than or equal to 1:100,greater than or equal to 1:75, greater than or equal to 1:50, greaterthan or equal to 1:40, greater than or equal to 1:25, greater than orequal to 1:16, greater than or equal to 1:10, greater than or equal to1:5, or greater than or equal to 1:3, greater than or equal to 1:1, orgreater. In some embodiments, the silica-based ceramic has asilicon-to-carbon molar ratio of less than or equal to 3,000:1, lessthan or equal to 2,000:1, less than or equal to 1,000:1, less than orequal to 500:1, less than or equal to 200:1, less than or equal to100:1, less than or equal to 75:1, less than or equal to 50:1, less thanor equal to 25:1, less than or equal to 10:1, less than or equal to 2:1,less than or equal to 1:1, or less. Combinations of these ranges arepossible. For example, in some embodiments, the silica-based ceramic hassilicon-to-carbon molar ratio of greater than or equal to 1:100 and lessthan or equal to 3.00:1, greater than or equal to 1:100 and less than orequal to 100:1, greater than or equal to 1:40 and less than or equal to10:1, or greater than or equal to 1:3 and less than or equal to 2:1.

The weight percentage and mole percentage and molar ratios in thesilica-based ceramic described above can be determined by removing thesilica-based ceramic from the rest of the anion exchange membrane ormaterial (e.g., porous support membrane, compressible edging materialetc.) and performing an elemental analysis, such as inductively coupledplasma mass spectrometry (ICP-MS) or nuclear magnetic resonance (NMR).

As mentioned above, in some embodiments, sol-gel techniques can be usedto form the silica-based ceramic. As such, in some cases, thesilica-based ceramic is sol-gel derived. In some embodiments, the solused in the sol-gel techniques is a silicon-containing precursor sol(i.e., the silica-based ceramic is derived from a silicon-containingprecursor sol). During fabrication of the anion exchange membrane, forexample, one or more components of the anion exchange membrane, such asa porous support membrane described herein, may be coated with thesilicon-containing precursor sol during at least one step of thefabrication process. The silicon-containing precursor sol may compriseany of a variety of suitable silicon-containing precursor components,such as silica colloidal particles, siloxanes, silicate esters,silanols, silanes, alkoxysilanes, tetraalkyl orthosilicates,halosilanes, or combinations thereof. In some embodiments, thesilica-based ceramic is derived from a silicon-containing precursor solcontaining two or more different silicon-containing precursorcomponents. In some such cases, the silica-based ceramic is formed via aco-condensation of two or more silicon-containing precursor components(e.g., two or more different silanes or substituted silanes).

In some embodiments, the silicon-containing precursor sol from which thesilica-based ceramic is derived comprises a silicon-containing precursorcomprising an ammonium group or a moiety comprising a leaving group(e.g., a halo group). In some embodiments, the silica-based ceramic isderived from a mixture (e.g., a silicon-containing precursor sol)comprising a silane (e.g., a substituted alkoxysilane) containingnitrogen (e.g., an ammonium). In some embodiments, the silica-basedceramic is derived from a mixture (e.g., a silicon-containing precursorsol) comprising a compound having structure (IV):

wherein R¹, R², and R³ are independently chosen fromoptionally-substituted, C₁₋₁₈ alkoxy and halo, L is chosen fromoptionally-substituted C₁₋₁₈ alkylene and arylene, and X is a leavinggroup. In some embodiments, each of R¹, R², and R³ is independentlychosen from optionally-substituted C₁₋₈ alkoxy and halo, L is chosenfrom optionally-substituted C₁₋₈ alkylene and arylene, and X is aleaving group. In some embodiments, each of R¹, R², and R³ areindependently chosen from optionally-substituted C₁₋₄ alkoxy and halo, Lis chosen from optionally-substituted C₁₋₄ alkylene and arylene, and Xis a leaving group. In some embodiments, X is chosen from chloro, bromo,iodo, tosyl, and trifluoromethanesulfonyl.

In some embodiments, the silica-based ceramic is derived from a mixture(e.g., a silicon-containing precursor sol) comprising a compound havingstructure (V):

wherein each A¹ is independently chosen from hydrogen, methyl, ethyl,propyl, or butyl, n is greater than or equal to 1 and less than or equalto 18, and X is a leaving group (e.g., a leaving group chosen fromchloro, bromo, iodo, tosyl, and trifluoromethanesulfonyl).

As one example, in some embodiments, the silica-based ceramic is derivedfrom a mixture (e.g., a silicon-containing precursor sol) comprising(3-chloropropyl)triethoxysilane (3CPTES). The resulting silica-basedceramic derived from the above-mentioned leaving group-containingcompounds may, in some cases, be reacted with an amine to form aquaternary ammonium group, as described in more detail below.

In some embodiments, the silica-based ceramic is derived from a mixture(e.g., a silicon-containing precursor sol) comprising a compound havingstructure (VI):

wherein R⁴, R⁵, and R⁶ are independently chosen fromoptionally-substituted C₁₋₁₈ alkoxy and halo, L is chosen fromoptionally-substituted C₁₋₁₈ alkylene and arylene, and R⁷, R⁸, and R⁹are independently chosen from optionally-substituted C₁₋₁₈ alkyl,cyclyl, and aryl. In some embodiments, each of R⁴, R⁵, and R⁶ isindependently chosen from optionally-substituted C₁₋₈ alkoxy and halo, Lis chosen from optionally-substituted C₁₋₈ alkylene and arylene, andeach of R⁷, R⁸, and R⁹ is independently chosen fromoptionally-substituted C₁₋₄ alkyl, cyclyl, and aryl. In someembodiments, each of R⁴, R⁵, and R⁶ is independently chosen fromoptionally-substituted C₁₋₄ alkoxy and halo, L is chosen fromoptionally-substituted C₁₋₄ alkylene and arylene, and each of R⁷, R⁸,and R⁹ is independently chosen from optionally-substituted C₁₋₄ alkyl,cyclyl, and aryl.

In some embodiments, the silica-based ceramic is derived from a mixture(e.g., a silicon-containing precursor sol) containing a compound havingstructure (VII):

where A² is independently chosen from hydrogen, methyl, ethyl, propyl,or butyl, n is greater than or equal to 1 and less than or equal to 18,and R¹⁰, R¹¹, and R¹² are independently chosen from methyl, ethyl,propyl, butyl, cyclohexyl, and benzyl.

As one example, in some embodiments, the silica-based ceramic is derivedfrom a mixture (e.g., a silicon-containing precursor sol) comprisingtrimethoxysilylpropyl-N,N,N-trimethylammonium (TMAPS). As anotherexample, in some embodiments, the silica-based ceramic is derived from amixture (e.g., a silicon-containing precursor sol) comprisingtriethoxysilylpropyl-N,N,N-trimethylammonium (TEAPS).

In some embodiments, the silica-based ceramic is derived from a mixture(e.g., a silicon-containing precursor sol) comprising a compound havingstructure (VIII):

wherein each R¹³ is independently chosen from hydrogen oroptionally-substituted C₁₋₁₈ alkyl. In some embodiments, each R¹³ isindependently chosen from hydrogen or optionally-substituted C₁₋₈ alkyl.In some embodiments, each R¹³ is independently chosen from hydrogen oroptionally-substituted C₁₋₄ alkyl. In some embodiments, each R⁷ isindependently chosen from methyl, ethyl, propyl and butyl.

In some embodiments, the silica-based ceramic is derived from a mixture(e.g., a silicon-containing precursor sol) comprising tetraethylorthosilicate (TEOS) and/or tetraethyl orthosiloxane. In someembodiments, the silica-based ceramic is derived from a single-phasemixture (e.g., a single-phase silicon-containing precursor sol)comprising both a compound having structure (VIII) (e.g., TEOS) and acompound having structure (IV) (e.g., (3-chloropropyl)triethoxysilane).In some embodiments, the silica-based ceramic is derived from a mixture(e.g., a silicon-containing precursor sol) comprising a compound havingstructure (VIII), a compound having structure (IV), and water in astructure (VIII):structure(IV):water molar ratio of 1:0.01-20:1-30, amolar ratio of 1:0.1-10:16, or a molar ratio of 1:0.25-1: 2-4. In someembodiments, the silica-based ceramic is derived from a single-phasemixture (e.g., a single-phase silicon-containing precursor sol)comprising both a compound having structure (VIII) (e.g., TEOS) and acompound having structure (VI) (e.g.,trimethoxysilylpropyl-N,N,N-trimethylammonium). In some embodiments, thesilica-based ceramic is derived from a mixture (e.g., asilicon-containing precursor sol) comprising a compound having structure(VIII), a compound having structure (VI), and water in a structure(VIII):structure(VI):water molar ratio of 1:0.01-10: 1-30, a molar ratioof 1:0.1-10: 2-20, or a molar ratio of 1:0.20-1: 2-15.

In some embodiments, the silica-based ceramic is derived from a mixture(e.g., a silicon-containing precursor sol) comprising two or moreprecursors. For instance, in some embodiments, the silica-based ceramicis derived from a mixture comprising a compound having structure (VIII)(e.g., TEOS) and a compound having structure (IV) (e.g.,(3-chloropropyl)triethoxysilane) in a structure (VIII):structure(IV)mass ratio of less than or equal to 99:1, less than or equal to 95:5,less than or equal to 90:10, less than or equal to 85:15, less than orequal to 80:20, less than or equal to 75:25, less than or equal to70:30, less than or equal to 65:35, less than or equal to 60:40, orless. In some embodiments, the silica-based ceramic is derived from amixture (e.g., a silicon-containing precursor sol) comprising a compoundhaving structure (VIII) (e.g., TEOS) and a compound having structure(IV) (e.g., (3-chloropropyl)triethoxysilane) in a structure(VIII):structure(IV) mass ratio of greater than or equal to 50:50,greater than or equal to 55:45, greater than or equal to 60:40, greaterthan or equal to 65:35, greater than or equal to 70:30, or greater.Combinations of these ranges are possible (e.g., greater than or equalto 50:50 and less than or equal to 99:1, greater than or equal to 60:40and less than or equal to 90:10, or greater than or equal to 70:30 andless than or equal to 80:20).

In some embodiments, the silica-based ceramic is derived from a mixture(e.g., a silicon-containing precursor sol) comprising a compound havingstructure (VIII) (e.g., TEOS) and a compound having structure (VI)(e.g., trimethoxysilylpropyl-N,N,N-trimethylammonium) in a structure(VIII):structure(VI) mass ratio of less than or equal to 99:1, less thanor equal to 95:5, less than or equal to 90:10, less than or equal to85:15, less than or equal to 80:20, less than or equal to 75:25, lessthan or equal to 70:30, less than or equal to 65:35, less than or equalto 60:40, or less. In some embodiments, the silica-based ceramic isderived from a mixture (e.g., a silicon-containing precursor sol)comprising a compound having structure (VIII) (e.g., TEOS) and acompound having structure (VI) (e.g.,trimethoxysilylpropyl-N,N,N-trimethylammonium) in a structure(VIII):structure(VI) mass ratio of greater than or equal to 40:60,greater than or equal to 45:55, greater than or equal to 50:50, greaterthan or equal to 55:45, greater than or equal to 60:40, greater than orequal to 65:35, greater than or equal to 70:30, or greater. Combinationsof these ranges are possible (e.g., greater than or equal to 40:60 andless than or equal to 99:1, greater than or equal to 60:40 and less thanor equal to 90:10, or greater than or equal to 70:30 and less than orequal to 80:20).

In some embodiments, the silica-based ceramic is derived from a mixture(e.g., a silicon-containing precursor sol) comprising an aqueoussolution having a certain pH, depending on the desired chemistry to beused. In some embodiments, the aqueous solution may have a pH of greaterthan or equal to −1, greater than or equal to 0, greater than or equalto 1, greater than or equal to 2, greater than or equal to 3, greaterthan or equal to 4, greater than or equal to 5, greater than the 6,greater than or equal to 7, greater than or equal to 8, greater than orequal to 9, or higher. In some embodiments, the aqueous solution mayhave a pH of less than or equal to 14, less than or equal to 13, lessthan or equal to 12, less than or equal to 11, less than or equal to 10,less than or equal to 9, less than or equal to 8, less than or equal to7, less than or equal to 6, less than or equal to 5, less than or equalto 4, less than or equal to 3, or less. Combinations of these ranges arepossible. For example, in some embodiments, the aqueous solution has apH of greater than or equal to −1 and less than or equal to 14, greaterthan or equal to 0 and less than or equal to 7, or greater than or equalto 1 and less than or equal to 3. In some cases, having a relativelyacidic pH (e.g., a pH of between 1-3) may allow for certain condensationand hydrolysis reactions to occur during fabrication of the anionexchange membrane involving the conversion of a sol-gel into asilica-based ceramic. In some embodiments, the silica-based ceramic isderived from a mixture described above (e.g. a silicon-containingprecursor sol) containing one or more acids such as, but not limited to,HCl, H₃PO₄, H₂SO₄, or HNO₃.

In some, but not necessarily all embodiments, the silica-based ceramicis derived from a mixture (e.g., a silicon-containing precursor sol)comprising one or more other solvents in addition to water. For example,in some embodiments, the silica-based ceramic is derived from a mixture(e.g., a silicon-containing precursor sol) comprising an alcohol. Insome such cases, the presence of an alcohol in the mixture can enhancethe miscibility of the components of the mixture. Exemplary alcoholsthat can be present include, but are not limited to, methanol, ethanol,isopropanol, butanol, or combinations thereof. In some embodiments, forexample, the silica-based ceramic is derived from a mixture (e.g., asilicon-containing precursor sol) comprising methanol (e.g., in somecases in which TMAPS is used as a precursor). In some embodiments, thesilica-based ceramic is derived from a mixture (e.g., asilicon-containing precursor sol) comprising one or more solvents thatmay be able to mitigate problems (e.g., cracking) that can occur during,for example, drying of a coating comprising the mixture to form thesilica-based ceramic. Exemplary solvents that, in some embodiments, maymitigate such problems include, but are not limiting to, formamide andaromatics (e.g., toluene, xylene).

As mentioned above, in some embodiments, the silica-based ceramic isporous. In some such embodiments, the silica-based ceramic is nanoporous(having pores with an average (mean) diameter of less than or equal to10 nm). The presence of relatively small pores in the silica-basedceramic may, in some cases, be advantageous in a number of applicationssuch as electrochemical applications and separation applications. Insome embodiments, the presence of relatively small pores in thesilica-based membrane ceramic can contribute to a relatively highselectivity of the anion exchange membrane (e.g., due to sizeexclusion). Relatively small pores may also contribute relatively highpermselectivity and a useful balance between anion conductivity (e.g.,chloride ion conductivity) and water transport. In some embodiments, thesilica-based ceramic has an average pore diameter of less than or equalto 1 μm (e.g., less than or equal to 500 nm, less than or equal to 100nm, or less than or equal to 50 nm). In some cases, the silica-basedceramic has an average pore diameter of less than or equal to 10 nm,less than or equal to 8 nm, less than or equal to 6 nm, less than orequal to 5 nm, less than or equal to 3 nm, less than or equal to 2 nm,or less. In some embodiments, the silica-based ceramic has an averagepore diameter of greater than or equal to 0.25 nm, greater than or equalto 0.4 nm, greater than or equal to 0.6 nm, or greater than or equal to1 nm. Combinations of these ranges are possible. For example, in someembodiments, the silica-based ceramic has an average pore diameter ofgreater than or equal to 0.25 nm and less than or equal to 1 μm, greaterthan or equal to 0.25 nm and less than or equal to 10 nm, greater thanor equal to 0.4 nanometers and less than or equal to 10 nm, greater thanor equal to 0.6 nm and less than or equal to 5 nm, or greater than orequal to 0.6 nm and less than or equal to 2.5 nm.

The average pore diameter of the silica-based ceramic may be determinedusing a small angle X-ray scattering (SAXS) technique. In a suitableSAXS technique, a collimated X-ray beam is focused onto a membranecomprising the silica-based ceramic for at least 15 minutes, and thescattering intensity as a function of scattering angle is collected onan image plate. The scattering intensity is integrated to generate a1-dimensional scattering profile that plots the scattering intensity asa function of the q-vector. Scattering of the membrane can be fit with asphere-based form factor (e.g., solid or core-shell). In some cases, thesphere-based form factor can include a structure factor (e.g., fractalor hard-sphere interactions). Fitting can be performed in the freelyavailable SASView software. A log-normal distribution on pore sizepolydispersity is assumed. A 1-D SAXS profile is assumed to be well-fitif the residual between the model and data set (Chi²) is less than orequal to 10, less than or equal to 1, less than or equal 0.5, or less.Certain parameters are held constant during fitting, includingSLD_(solvent)=18.8×10⁻⁶ k² and SLD_(sphere)=0 Å⁻², where SLD is thescattering length density. SAXS fitting can be used to determine thevolume fraction of porosity, pore size (e.g., average pore diameter),and polydispersity index of the pore size distribution. Suitable SAXSprocedures are described in more detail, for example, in Pedersen, J.S., Analysis of small-angle scattering data from colloids and polymersolutions: modeling and least-squares fitting. Advances in Colloid andInterface Science 1997, 70, 171-210, and in Zemb., T.; Lindner, P.,Neutron, X-Rays and Light. Scattering Methods Applies to Soft CondensedMatter. North Holland: 2002, which are incorporated herein by referencein their entirety. The average pore diameter may also be determinedusing other small angle scattering techniques, such as small angleneutron scattering (SANS).

In some embodiments, the anion exchange membrane or material has arelatively large volumetric porosity. The volumetric porosity may dependon the porosity of the silica-based ceramic. Having a relatively highvolumetric porosity may contribute to certain beneficial performancecharacteristics of the anion exchange membrane, such as an anionexchange capacity and water uptake. In some embodiments, the anionexchange membrane or material has a volumetric porosity of greater thanor equal to 1%, greater than or equal to 3%, greater than or equal to5%, greater than or equal to 10%, greater than or equal to 20%, greaterthan or equal to 30%, greater than or equal to 40%, or more. In someembodiments, the anion exchange membrane or material has a volumetricporosity of less than or equal to 70%, less than or equal to 60%, lessthan or equal to 50%, less than or equal to 45%, less than or equal to40%, less than or equal to 35%, less than or equal to 30%, less than orequal to 25%, less than or equal to 15%, or less. Combinations of theseranges are possible. For example, in some embodiments, the anionexchange membrane or material has a volumetric porosity of greater thanor equal to 1% and less than or equal to 70%, greater than or equal to5% and less than or equal to 50%, greater than or equal to 10% and lessthan or equal to 50%, or greater than or equal to 30% and less than orequal to 50%. As mentioned above, these volumetric porosities of theanion exchange membrane or material are determined via fitting of SAXSdata of the anion exchange membrane or material.

In some embodiments, the pores of the silica-based ceramic have arelatively small aspect ratio (length:width). Aspect ratio of the poresof the silica-based membrane can be determined by fitting SAXS data toan ellipsoid model to determine an average first radius and an averagesecond radius of the pores of the silica-based membrane, and taking theratio of the average first and the average second radius. In someembodiments, the pores of the silica-based membrane have an aspect ratioof less than or equal to 40:1, less than or equal to 20:1, less than orequal to 10:1, less than or equal to 5:1, or less.

In some embodiments, the pores of the silica-based ceramic have anordered structure. Such an ordered structure may, in some cases,contrast with the pores of certain existing anion exchange membrane suchas those made from hydrocarbon- or perfluorocarbon-based polymers, whichcan have worm-like, disordered pores (e.g., with a high polydispersity).Having a silica-based ceramic with regular, ordered pores over arelatively large size scale can, in some cases, correspond to improvedperformance characteristics in anion exchange applications. The pores ofthe silica-based ceramic have an ordered structure if the scatteringdata from a SAXS experiment on a membrane or material containing thesilica-based ceramic can be fit to a mathematical model, such as afractal aggregate model, with a Chi²/N value of less than or equal to10, less than or equal to 5, less than or equal to 1, less or equal to0.5, or less, where Chi² is a squared sum of an intensity differencebetween the mathematical model and the small angle scattering spectradata, and N is the number of points small-angle scattering data pointsover a model fitting range. An exemplary fractal aggregate model usingSAXS data of intensity (I) as a function of a scattering vector, q, isas follows:

I(q)=P(q)S(q)+bck

S(q) is a network or fractal structure that defines an organization orconfiguration of building blocks of the network of pores of thesilica-based ceramic. In other words, in some embodiments, the buildingblocks are the pores of the silica-based ceramic. Bck defines backgroundscattering, such as from a scattering particle source and/or inelasticscattering of scattering particles off of the silica-based ceramic. Insome embodiments, S(q) is defined by the following equation:

${S(q)} = {1 + {\frac{D_{f}{\Gamma \left( {D_{f} - 1} \right)}}{\left. \left\lbrack {1 + {{1/q}\; \xi}} \right)^{2} \right\rbrack^{{({D_{f} - 1})}/2}}\frac{\sin \left\lbrack {\left( {D_{f} - 1} \right){\tan^{- 1}\left( {q\; \xi} \right)}} \right\rbrack}{\left( {qR_{0}} \right)^{D_{f}}}}}$

where

R_(o) is a radius of the building blocks (pores), ρ_(solvent) is ascattering length density of a solvent (the silica-based ceramic),ρ_(block) is a scattering length density of the building blocks (assumedto be the scattering length density of air at ambient conditions if themembrane is dry), D_(f) is a fractal dimension, ξ is a correlationlength, and Γ is the standard mathematical gamma function.

P(q) is a form factor that defines a structure of the building blocks ofthe network of pores of the silica-based ceramic as a function of q.Such form factors may take on a variety of shapes, such as simplegeometric shapes like spheres, ellipsoids, cubes, ovals, and the like.

In some embodiments, the building blocks (pores) are defined ashomogeneous building blocks, such as homogeneous spheres. In thatregard, in some embodiments, P(q) is defined by the following equation:

P(q) = scale × V(ρ_(block) − ρ_(solvent))²F(qR₀)², where${{F(x)} = \frac{3\left\lbrack {{\sin (x)} - {x{\cos (x)}}} \right\rbrack}{x^{3}}},{V = {\frac{4}{3}\pi R_{0}^{3}}},$

and scale is a volume fraction of building blocks of the measuredsilica-based ceramic.

In some embodiments, the form factor defines a spherical core-shellbuilding block (pore). In some such embodiments, regard, P(q) is definedby the following formula:

${P(q)} = {{\frac{scale}{V_{s}}\left\lbrack {{3\; {V_{c}\left( {\rho_{c} - \rho_{s}} \right)}\frac{\left\lbrack {{\sin \left( {qr}_{c} \right)} - {{qr}_{c}{\cos \left( {qr}_{c} \right)}}} \right\rbrack}{\left( {qr}_{c} \right)^{3}}} + \mspace{259mu} {3{V_{s}\left( {\rho_{s} - \rho_{block}} \right)}\frac{\left\lbrack {{\sin \left( {qr}_{s} \right)} - {{qr}\; \cos \; \left( {qr}_{s} \right)}} \right\rbrack}{\left( {qr}_{s} \right)^{3}}}} \right\rbrack}^{2} + {bkg}}$

where

scale is a volume fraction of building blocks of the measuredsilica-based ceramic, V_(c) is a volume of the core, V_(s) is a volumeof the shell, p_(c) is a scattering length density of the core, p_(s) isa scattering length density of the shell (e.g., shell of functionalgroups), ρ_(block) is a scattering length density of the building blocks(pores), r_(c) is a radius of the core, r_(s) is a radius of the shell,and bck is background scattering.

In some embodiments, one or more surfaces of the silica-based ceramicare coated with an additional coating. A core-shell model, such as thecore-shell fractal aggregate model may be suitable to characterizecore-shell particle building blocks. In some cases, a core-shell modelis suitable even in the absence of an additional coating process. Forexample, in some embodiments, the method used to form the silica-basedceramic (e.g., a sol-gel based method) produces phase segregated regionsthat can be modeled using a core-shell model.

As above, various embodiments of the form factors, P(q), of the fractalaggregate models used to characterize small-angle scattering spectra caninclude a factor that accounts for differences between scattering lengthdensities.

In some embodiments, scattering length densities in the above equationsare defined by the materials that make up the components of thesilica-based ceramic membranes. Generally, larger differences betweenscattering length densities of scattering sources, such as pores, andsurrounding ceramic materials provide larger scattering contrast.Accordingly, in some embodiments, small-angle scattering data isgenerated from silica-based ceramics that have been dried to removesolvent or other liquid from the pores, thus providing a greaterdifference in scattering length densities compared to a silica-basedceramic with pores filled with a liquid solvent.

In some embodiments, the scattering length densities are defined inunits of Å⁻² (inverse angstroms squared). The scattering length densityis defined as the sum of the bound coherent scattering length of eachatom normalized by the molecular volume. For example, the X-rayscattering length density of air is roughly 0 Å⁻² while x-ray scatteringlength density of amorphous silica is roughly 18.8×10⁻⁶ Å⁻².

In some embodiments, small-angle scattering data is generated fromsilica-based ceramic that have been rinsed to remove residual ions,chemical reactants, and the like.

In some embodiments, fitting small-angle scattering spectra to a fractalaggregate model includes fitting the small-angle scattering spectra overa range of q values that exceeds an order of magnitude, such as over anorder of magnitude where q is in units of Å⁻¹. Such a relatively widefitting range may ensure that the data is fit to the fractal aggregatemodel over a range of sizes commensurate in scope with, for example, asize scale of pores of the silica-based ceramic, in addition toproviding data sufficient to fit with the fractal aggregate model. Insome embodiments, fitting small-angle scattering spectra to a fractalaggregate model includes fitting the small-angle scattering spectra overa range of q values in a range of about 0.01 Å⁻¹ to about 1 Å⁻¹. In someembodiments, fitting small-angle scattering spectra to a fractalaggregate model includes fitting the small-angle scattering spectra overa range of q values in a range of about 0.02 Å⁻¹ to about 0.8 Å⁻¹.

As above, scale corresponds to a volume fraction of pores in thesilica-based ceramic. In some embodiments, scale corresponds to membraneporosity when the small-angle scattering spectra are in intensity unitsof 1/cm and the scale is less than 0.7. In this regard, the scalecorresponds to a number of pores, normalized by a size of the sample. Insome embodiments, the silica-based ceramic has a porosity volumefraction in a range of about 0.01 to about 0.7. In some embodiments, thesilica-based ceramic has a porosity volume fraction in a range of about0.15 to about 0.35. It should be understood that the above-mentionedranges correspond to cases in which the scattering length density refersto that of air at ambient conditions for the pores and amorphous silicafor the silica-based ceramic, respectively.

In some embodiments, D_(f) is a fractal dimension of the fractalaggregate models described herein. In some embodiments, D_(f)corresponds to a shape and/or configuration of pores within thesilica-based ceramic. Generally, D_(f) is in a range of about 1 to about3. Where D_(f) is close to or at 1, the pores may be generallycharacterized as 1-dimensional tunnels. Where D_(f) is close to or at 3,the pores may be generally characterized as open spheres.

In some embodiments, it is advantageous to have a silica-based ceramicdefining pores having a tortuous or indirect route through thesilica-based ceramic. For an ion or other particle in fluidcommunication with a tortuous pore, it is less likely that the ion orother particle will traverse the membrane as a size of the ion or otherparticle approaches that of the tortuous pore than compared to a lesstortuous pore. In that regard, such silica-based ceramics definingtortuous pores may, in some cases, be suitable to provide, for example,more selective anion exchange than, for example, silica-based ceramicsdefining pores of the same size, but that provide a more direct paththrough the silica-based ceramic. In this regard, in some, but notnecessarily all embodiments D_(f) is in a range of 2.0-4.0. Such D_(f)ranges describe or characterize silica-based ceramics having relativelytortuous pores having a form factor somewhere between a straight lineand an open sphere.

In some embodiments, the fractal aggregate model is constrained to havepore sizes within a particular range. As above, the porous supportdefines pores with an average pore diameter within the ranges describedabove. Likewise, the methods described in the present disclosure aresuitable to make such silica-based ceramics defining pores in such asize range. Accordingly, by constraining fractal aggregate models usedto fit small-angle scattering data, a good fit between the fractalsilica-based ceramic and the fractal aggregate model can be obtained.

As above, the correlation length, ξ, is a length over which the fractalpattern of the silica-based ceramic repeats itself. In some cases,silica-based ceramics will repeat the fractal pattern over a relativelylarge size scale. In this regard, such silica-based ceramics defineregular, ordered pores over a relatively large size scale, which may, insome cases, correspond to improved functional properties, such asfiltration, ion exchange, and the like. Analogously, a fractal patterngenerally cannot extend to size scales smaller than a size scale ofbuilding blocks of the silica-based ceramic, such as smaller thanmolecules or atoms. Accordingly, in some embodiments, the correlationlength, ξ, is constrained to a value of greater than 1 nm. In someembodiments, the correlation length, ξ, is constrained to a value ofgreater than 50 nm. In some embodiments, the correlation length, ξ, isconstrained to a value of greater than 100 nm. In some embodiments, thecorrelation length, ξ, is constrained to a value of about a thickness ofthe silica-based ceramic. In some embodiments, the silica-based ceramicshave a correlation length, ξ, greater than 1 nm, such as greater than 50nm or greater than 100 nm.

The fractal aggregate models used to characterize the silica-basedceramic may include terms to account for variability in sizes ofscattering sources, such as the pores of the silica-based ceramic. Inthat regard, in some embodiments, the fractal aggregate model includes apolydispersity index in a radius parameter. Accordingly, in someembodiments a radius of a building block, R_(o), is a weighted averagerather than a constant. The weighted average may be according to anumber of mathematical functions, such a Gaussian function, a log-normalfunction, a rectangular distribution, and the like. In some embodiments,the polydispersity index is Gaussian and according to the equation:

${f(x)} = {\frac{1}{Norm}{\exp\left( {- \frac{\left( {x - x_{mean}} \right)^{2}}{2\sigma^{2}}} \right)}}$

where x_(mean) is a mean value of the distribution (average radius),Norm is a normalization factor determined during numerical calculation,and the polydispersity index is the ratio of σ/x_(mean).

In some embodiments, the polydispersity ratio is log-normal andaccording to the equation:

${f(x)} = {\frac{1}{Norm}\frac{1}{xp}\exp \; \left( {- \frac{\left( {{\ln \; (x)} - \mu} \right)^{2}}{2p^{2}}} \right)}$

where p is the polydispersity index, μ=ln(x_(med)), x_(med) is a medianvalue of the distribution, and Norm is a normalization factor determinedduring numerical calculation.

In some embodiments, log-normal distributions are advantageous as theyare generally not symmetric about x_(med). In this regard, as thepolydispersity ratio increases, the lower tail may not fall into rangesthat are aphysical, such as those which would define a pore size smallerthan, for example, atoms, etc. that physically define the pores.

In some embodiments, the pores of the silica-based ceramic have arelatively low log-normal polydispersity index of pore radius. Having arelatively low log-normal polydispersity index of pore radius generallycorresponds to the pores having relatively similar radii, which may beindicative of a regular, ordered structure to the pores of thesilica-based ceramic. In some embodiments, the pores of the silica-basedceramic have a log-normal polydispersity index of pore radius of lessthan or equal to 0.8, less than or equal to 0.7, less than or equal to0.5, less than or equal to 0.3, or less. In some embodiments, the poresof the silica-based ceramic have a log-normal polydispersity index ofgreater than or equal to 0 and less than or equal to 0.8, greater thanor equal to 0 and less than or equal to 0.7, greater than or equal to 0and less than or equal to 0.5, in greater than or equal to 0 and lessthan or equal to 0.3.

In some embodiments, the pores of the silica-based ceramic fit aTeubner-Strey model. The Teubner-Strey model was originally developed todescribe the scattering patterns and microstucture of microemulsions(e.g., mixtures of water, oil, and amphiphiles). Small angle scatteringexperiments such as small angle neutron scattering (SANS) experimentshave revealed herein that, unexpectedly, in embodiments, ion exchangemembranes or materials have a silica-based ceramic pore structure thatfits such a Teubner-Strey model. A Teubner-Strey ordering is morecommonly associated with packed micellar structures where the micellesenforce well-defined pore structures and pore-pore distances, ratherthan in ceramic-based structures observed herein.

When the pores of the silica-based ceramic fit a Teubner-Strey model ofsmall angle scattering spectra, the intensity (I) as a function of ascattering vector, q, fits the following equation:

${I(q)} = {\frac{1}{a + {c_{1}q^{2}} + {c_{2}q^{4}}} + {bck}}$

where a, c₁, and c₂ are adjustable parameters and bck is backgroundscattering. The pores of the silica-based ceramic may fit aTeubner-Strey model if the scattering data from a small angle scatteringexperiment (e.g., small angle neutron scattering, SANS) on a membrane ormaterial containing the silica-based ceramic can be fit to aTeubner-Strey model with a Chi²/N value of less than or equal to 10,less than or equal to 5, less than or equal to 1, less or equal to 0.5,or less, where Chi³ is a squared sum of an intensity difference betweenthe mathematical model and the small angle scattering spectra data, andN is the number of points small-angle scattering data points over amodel fitting range. N may be, for example, at least 30, at least 50, atleast 100, at least 200, at least 500, and/or up to 1,000, up to 2,000or more points over a model fitting range. In some embodiments, themodel fitting range for q is from 0.01 Å⁻¹ to 1 Å⁻¹, or from 0.07 Å⁻¹ to0.7 Å⁻¹.

A Teubner-Strey fitting of small angle scattering of pores of thesilica-based ceramic may also afford measurements of the domain size, d,(periodicity) and correlation length, ξ, according to the followingequations:

${I(q)} = \frac{{\left( {8\pi} \right)/\xi}{\langle\eta^{2}\rangle}c_{2}}{a + {c_{1}q^{2}} + {c_{2}q^{4}}}$${\gamma (r)} = {\frac{\sin \; {kr}}{kr}e^{{- r}/\xi}}$$\xi = \left\lbrack {{\frac{1}{2}\left( \frac{a}{c_{1}} \right)^{\frac{1}{2}}} + \left( \frac{c_{1}}{4c_{2}} \right)} \right\rbrack^{- \frac{1}{2}}$$\frac{d}{2\pi} = \left\lbrack {{\frac{1}{2}\left( \frac{a}{c_{1}} \right)^{\frac{1}{2}}} - \left( \frac{c_{1}}{4c_{2}} \right)} \right\rbrack^{- \frac{1}{2}}$

where

η²

is the mean square to the fluctuation in scattering density of themedia, γ(r) is the real-space correlation function corresponding toI(q), and k=2π/d. In the context of the anion exchange membranes ormaterials, ξ is equivalent to the radius of the pores of thesilica-based ceramic, and d is equivalent to the pore-pore distancemeasured from the center of two separate nearest-neighbor pores of thesilica-based ceramic. Further description of the Teubner-Strey model andits application to small angle scattering measurements can be found inSchubert, K. V., Strey, R., Kline, S. R., & Kaler, E. W. (1994). Smallangle neutron scattering near Lifshitz lines: Transition from weaklystructured mixtures to microemulsions. The Journal of Chemical Physics,101(6), 5343-5355., and Teubner, M., & Strey, R. (1987). Origin of thescattering peak in microemulsions. The Journal of Chemical Physics,87(5), 3195-3200, each of which is incorporated herein by reference inits entirety for all purposes.

In some, but not necessarily all embodiments, the structure of the poresof the silica-based ceramic depends on a state of the anion exchangemembrane or material. For example, whether the anion exchange is in adry state or a hydrated state can in some instances affect the porestructure of the silica-based ceramic. The pores of a silica-basedceramic may fit a first mathematical model of small angle scatteringspectra when the anion exchange membrane or material is in a first state(e.g., a dry state), and the pores of a silica-based ceramic may fit asecond, different mathematical model of small angle scattering spectrawhen the anion exchange membrane or material is in a second, differentstate (e.g., a hydrated state). In this context, an anion exchangemembrane or material is considered to be in a dry state when it has beenheated in an oven at 100° C. and 0% relative humidity for 2 hours, andan anion exchange membrane or material is considered to be in a hydratedstate when it is submerged in H₂O or D₂O at room temperature for 24hours in a vacuum environment having a reduced pressure to pull air outof the pores but that is not low so low as to cause the H₂O or D₂O toboil.

As another example, in some but not necessarily all embodiments, theaverage pore diameter of the silica-based ceramic is larger when theanion exchange membrane or material is in a hydrated state as comparedto when the anion exchange membrane or material is in a dry state. Ithas been observed that having an average pore diameter in a hydratedstate that is greater than an average pore diameter in a dry state canresult in a percolation of hydrated domains in the silica-based ceramic.Such percolation can result in improved anion transport properties(e.g., chloride ion conductivity). In some embodiments, the silica-basedceramic has an average pore diameter that is larger when the anionexchange membrane is in a hydrated state than when the anion exchangemembrane is in a dry state by a factor of greater than or equal to 1.1,greater than or equal to 1.2, greater than or equal to 1.3, greater thanor equal to 1.4, greater than or equal to 1.5, greater than or equal to1.6, greater than or equal to 1.8, greater than or equal to 2, orgreater. In some embodiments, the silica-based ceramic has an averagepore diameter that is larger when the anion exchange membrane is in ahydrated state than when the anion exchange membrane is in a dry stateby a factor of less than or equal to 5, less than or equal to 4.5, lessthan or equal to 4, less than or equal to 3.5, less than or equal to 3,less than or equal to 2.8, less than or equal to 2.6, less than or equalto 2.5, less than or equal to 2.4, less than or equal to 2.3, less thanor equal to 2.2, less than or equal to 2.1, less than or equal to 2, orless, Combinations of these ranges are possible. For example, in someembodiments, the silica-based ceramic has an average pore diameter thatis larger when the anion exchange membrane is in a hydrated state thanwhen the anion exchange membrane is in a dry state by a factor ofgreater than or equal to 1.1 and less than or equal to 5, or greaterthan or equal to 1.3 and less than or equal to 3.

As another example, in some but not necessarily all embodiments, thepores of a silica-based ceramic fit a Teubner-Strey model of small anglescattering spectra as described above when the anion exchange membraneor material is in a dry state, and the pores of a silica-based ceramicfit a core-shell model of small angle scattering spectra as describedabove when the anion exchange membrane or material is in a hydratedstate. It has been observed that in some embodiments, having aTeubner-Strey ordering in a dry state and a core-shell structure in ahydrated state is associated with structural changes upon water-intakethat impart beneficial performance properties (e.g., anion exchangecapacity, anion conductivity, permselectivity, etc.).

In some embodiments, the pore structure of a silica-based membranedepends on a state of the anion exchange membrane or material can dependon the composition of the silica-based membrane or material and/or theconditions under which the anion exchange membrane or material was made.For example, the dependence of the pore structure on a state of theanion exchange membrane or material (e.g., when dry vs. when hydrated)may depend on an amount of functional groups (e.g., quaternary ammoniumgroups) present in the silica-based ceramic. The amount of functionalgroups present may in turn depend on ratios of silicon-containingprecursors in, for example, a silicon-containing precursor sol duringfabrication of the anion exchange membrane or material. In someembodiments, anion exchange membranes derived from silicon-containingprecursor sols having relatively low amounts (e.g., less than or equalto 5 mol %, less than or equal to 1 mol %, or less) ofsilicon-containing precursors comprising functional groups (e.g., havingstructure IV or VI) have a pore structure (e.g., average pore diameter,small angle scattering model fit) that is relatively similar whether theanion exchange membrane or material is in a dry state or in a hydratedstate. For example, in some such instances the average pore diameter ina hydrated state is within 10%, within 5%, or within 2% of the averagepore diameter in the dry state. However, in some embodiments, anionexchange membranes derived from silicon-containing precursor sols havingrelatively high amounts (e.g., greater than or equal to 15 mol %,greater than or equal to 20 mol %, greater than or equal to 25 mol %,greater than or equal to 30 mol %, greater than or equal to 35 mol %,greater than or equal to 40 mol %, or greater) of silicon-containingprecursors comprising functional groups (e.g., having structure IV orVI) have a pore structure (e.g., average pore diameter, small anglescattering model fit) that is substantially different (e.g., porediameters in a hydrated state greater than pore diameters in a dry stateby a factor of greater than or equal to 1.1, greater than or equal to1.2, greater than or equal to 1.3, greater than or equal to 1.4, greaterthan or equal to 2, or greater) when the anion exchange membrane ormaterial is in a dry state versus when it is in a hydrated state.

As mentioned above, in some embodiments, the anion exchange membranecomprises a porous support membrane. The porous membrane (e.g., poroussupport membrane 130) may comprise any of a variety of suitablematerials and may be in any of a variety of forms.

In some embodiments, the porous support membrane comprises relativelylarge pores in the absence of the silica-based ceramic, such as prior tobeing coated with the silica-based ceramic. For example, referring backto FIG. 2A, porous support membrane 130 comprises pores that includepore 132, which is relatively large. Having relatively large pores may,in some embodiments, allow for sufficient overall permeability acrossthe membrane as well as sufficient space for the silica-based ceramic tobe present in cases in which a coating formed by the silica-basedceramic is located at least partially within the porous membranesupport. In some embodiments, the porous support membrane comprisespores having an average (mean) pore diameter, in the absence of thesilica-based ceramic, such as prior to being coated with thesilica-based ceramic, of greater than or equal to 50 nm, greater than orequal to 75 nm, greater than or equal to 100 nm, greater than or equalto 200 nm, greater than or equal to 500 nm, greater than or equal to 1μm, greater than or equal to 2 μm, greater than or equal to 5 μm,greater than or equal to 10 μm, greater than or equal to 15 μm, greaterthan or equal to 20 μm, greater than or equal to 30 μm, greater than orequal to 40 μm, or more. However, in some embodiments, the poroussupport membrane does not comprise pores that are so large as to causedeleterious effects on the performance or properties of the anionexchange membrane (e.g., poor mechanical burst strength, low retentionof coating, etc.). In some embodiments, the porous support membranecomprises pores having an average pore diameter, in the absence of thesilica-based ceramic, such as prior to being coated with thesilica-based ceramic, of less than or equal to 50 μm, less than or equalto 25 μm, less than or equal to 10 μm, less than or equal to 5 μm, lessthan or equal to 2 μm, less than or equal to 1 μm, less than or equal to500 nm or less. Combinations of these ranges are possible. For example,in some embodiments, the porous support membrane comprises pores havingan average diameter, in the absence of the silica-based ceramic, such asprior to being coated with the silica-based ceramic, of greater than orequal to 50 nm and less than or equal to 50 μm, greater than or equal to500 nm and less than or equal to 10 μm, or greater than or equal to 1 μmand less than or equal to 5 μm. The average pore diameter of the poroussupport membrane in the anion exchange membrane can be determined byBrunauer-Emmett-Teller (BET) gas sorption techniques or mercuryintrusion porosimetry.

It should be understood that in some embodiments, the silica-basedceramic, when present fills at least a portion (or all) of the pores ofthe porous support membrane. In such cases, the average pore diameter ofthe porous support membrane in the final anion exchange membrane will besmaller than the average pore diameter of the porous support membraneprior to being coated by the silica-based ceramic. Additionally and asmentioned above, in some embodiments, the silica-based ceramic itself isporous (e.g., nanoporous). As such, in some embodiments, the anionexchange membrane has a bimodal distribution of pores. For example, insome embodiments the anion exchange membrane has a bimodal distributionof pores comprising relatively small pores that correspond to the poresof the silica-based ceramic and relatively large pores that correspondto the partially-filled (e.g., 70%-filled) pores of the porous supportmembrane. In these embodiments, the bimodal distribution can bedetermined by measuring the relatively small pores using the SAXStechniques described above (e.g., to measure the pores that correspondto the silica-based ceramic), and measuring the relatively large poresusing the BET gas sorption or mercury intrusion porisimetry techniquesdescribed above (e.g., to measure the pores that correspond topartially-filled pores of the porous support membrane).

In some embodiments, the relatively small pores of the bimodaldistribution (e.g., that correspond to the pores silica-based ceramic)have an average pore diameter of less than or equal to 1 μm (e.g., lessthan or equal to 500 nm, less than or equal to 100 nm, or less than orequal to 50 nm). In some cases, the relatively small pores of thebimodal distribution (e.g., that correspond to the pores silica-basedceramic) have an average pore diameter of less than or equal to 10 nm,less than or equal to 8 nm, less than or equal to 6 nm, less than orequal to 5 nm, less than or equal to 3 nm, less than or equal to 2 nm,or less. In some embodiments, the relatively small pores of the bimodaldistribution (e.g., that correspond to the pores silica-based ceramic)have an average pore diameter of greater than or equal to 0.25 nm,greater than or equal to 0.4 nm, greater than or equal to 0.6 nm, orgreater than or equal to 1 nm. Combinations of these ranges arepossible. For example, in some embodiments, the relatively small poresof the bimodal distribution (e.g., that correspond to the poressilica-based ceramic) have an average pore diameter of greater than orequal to 0.25 nm and less than or equal to 1 μm, greater than or equalto 0.25 nm and less than or equal to 10 nm, greater than or equal to 0.4nanometers and less than or equal to 10 nm, greater than or equal to 0.6nm and less than or equal to 5 nm, or greater than or equal to 0.6 nmand less than or equal to 2.5 nm.

In some embodiments, the relatively large pores of the bimodaldistribution (e.g., that correspond to the partially-filled pores of theporous support membrane) have an average pore diameter of greater thanor equal to 50 nm, greater than or equal to 75 nm, greater than or equalto 100 nm, greater than or equal to 200 nm, greater than or equal to 500nm, greater than or equal to 1 μm, greater than or equal to 2 μm,greater than or equal to 5 μm, greater than or equal to 10 μm, greaterthan or equal to 15 μm, greater than or equal to 20 μm, greater than orequal to 30 μm, greater than or equal to 40 μm, or more. In someembodiments, the relatively large pores of the bimodal distribution(e.g., that correspond to the partially-filled pores of the poroussupport membrane) have an average pore diameter of less than or equal to50 μm, less than or equal to 25 μm, less than or equal to 10 μm, lessthan or equal to 5 μm, less than or equal to 2 μm, less than or equal to1 μm, less than or equal to 500 nm or less. Combinations of these rangesare possible. For example, in some embodiments, the relatively largepores of the bimodal distribution (e.g., that correspond to thepartially-filled pores of the porous support membrane) have an averagepore diameter of greater than or equal to 50 nm and less than or equalto 50 μm, greater than or equal to 500 nm and less than or equal to 10μm, or greater than or equal to 1 μm and less than or equal to 5 μm.

In some embodiments, the porous support membrane has a relatively highvolumetric porosity in the absence of the silica-based ceramic, such asprior to being coated with the silica-based ceramic. Having a relativelyhigh volumetric porosity may, in some cases, allow for sufficientoverall permeability as well as sufficient space for the silica-basedceramic to be present in cases in which a coating formed by thesilica-based ceramic is located at least partially within the porousmembrane support. In some embodiments, the porous support membrane, inthe absence of the silica-based ceramic, such as prior to being coatedwith the silica-based ceramic, has a volumetric porosity of greater thanor equal to 10%, greater than or equal to 15%, greater than or equal to20%, greater than or equal to 30%, greater than or equal to 40, greaterthan or equal to 50%, greater than or equal to 60%, greater than orequal to 70%, greater than or equal to 80%, greater than or equal to90%, or higher. In some embodiments, the porous support membrane has avolumetric porosity, in the absence of the silica-based ceramic, such asprior to being coated with the silica-based ceramic, of less than orequal to 99%, less than or equal to 95%, less than or equal to 90%, lessthan or equal to 80%, less than or equal to 70%, less than or equal to60%, less than or equal to 50%, less than or equal to 40%, less than orequal to 30%, or less. Combinations of these ranges are possible. Forexample, in some embodiments, the porous support membrane, in theabsence of the silica-based ceramic, such as prior to being coated withthe silica-based ceramic, has a volumetric porosity of greater than orequal to 10% and less than or equal to 99%, greater than or equal to 50%and less than or equal to 99%, greater than or equal to 80% and lessthan or equal to 99%, or greater than or equal to 60% and less than orequal to 80%. It should be understood that in some embodiments, thesilica-based ceramic fills at least a portion of the pores of the poroussupport membrane. Therefore, in some embodiments, the overall anionexchange membrane may have a volumetric porosity that is different thanthe volumetric porosity of the porous support membrane in the absence ofthe silica-based ceramic. The volumetric porosity of the porous supportmembrane in the anion exchange membrane can be determined by BET gassorption techniques or mercury intrusion porosimetry.

The porous support membrane may have any suitable cross-sectionalthickness. Having a suitable cross-sectional thickness can, in somecases, allow for the porous support membrane and ultimately the anionexchange membrane to have suitable mechanical properties (e.g.,mechanical burst strength) and performance characteristics (e.g., byhaving an appropriate permeability and ion transport rate). In someembodiments, the porous support membrane has a cross-sectional thicknessof greater than or equal to 3 μm, greater than or equal to 5 μm, greaterthan or equal to 10 μm, greater than or equal to 25 μm, greater than orequal to 50 μm, greater than or equal to 75 μm, greater than or equal to100 μm, greater than or equal to 150 μm, greater than or equal to 200μm, greater than or equal to 300 μm, greater than or equal to 400 μm,greater than or equal to 500 μm, or more. In some embodiments, theporous support membrane has a cross-sectional thickness of less than orequal to 1,000 μm, less than or equal to 500 μm, less than or equal to300 μm, less than or equal to 100 μm, or less. Combinations of theseranges are possible. For example, in some embodiments, the poroussupport membrane has a cross-sectional thickness of greater than orequal to 3 μm and less than or equal to 1,000 μm, or greater than orequal to 25 μm and less than or equal to 300 μm. The cross-sectionalthickness of the porous support membrane in the anion exchange membranecan be determined using SEM/EDX techniques on the anion exchangemembrane. In some embodiments, the EDX component of the technique can beused to distinguish between the porous support membrane and othercomponents of the anion exchange membrane, such as the silica-basedceramic.

The porous support membrane can be in the any of a variety of suitableforms. It should therefore be understood that the depiction of poroussupport membrane 130 in FIG. 2A is non-limiting and exemplary, and thatporous support membrane 130 can be in the form of any suitablestructure. In some embodiments, the porous support membrane may be inthe form of a macroporous structure. For example, in some embodiments,the porous support membrane is in the form of a non-woven fabric or anon-woven mesh. In some embodiments, the porous support membrane is inthe form of a veil. In some embodiments, the porous support membrane isin the form of a knit fabric. In some cases, the porous support membraneis in the form of a woven fabric or mesh. In some embodiments, theporous support membrane is in the form of an open-cell structure, suchas an open-cell foam. In some embodiments, the porous support membraneis in the form of a fibril and node structure. In some cases, the poroussupport membrane includes combinations of multiple types of microporousstructures. For example, in some embodiments, the porous supportmembrane includes combinations of the exemplary structures describedabove (e.g., non-woven fabric, open-cell foam, etc.).

The porous support membrane may be formed by any suitable method. Insome embodiments, the porous support membrane is a wet-laid structure ora non-wet-laid structure (e.g., an airlaid structure, a cardedstructure, a meltblown structure, a meltspun structure (e.g., spunbond),a centrifugal spun web, a solvent spun web, an electroblown web, a gelspun web).

As mentioned above, in some embodiments, the porous support membranecomprises support components. The support components of the poroussupport membrane generally refer to the components of the porous supportmembrane that contribute to the overall structure and mechanicalproperties of the porous support membrane. For example, in someembodiments in which the porous support membrane is in the form of anon-woven fabric, the support components of the non-woven fabric mayinclude the fibers and/or filaments from which the non-woven fabric isformed. As another example, in some embodiments in which the poroussupport membrane is in the form of a mesh, the support components of themesh may include the strands of which the mesh is formed. Examples ofsupport components include, but are not limited to, fibers, strands, andwires. Referring again to FIG. 2A, porous support membrane 130 comprisesan exemplary porous support component 135, according to someembodiments.

In some embodiments, the support components have a relatively largenumber average diameter. In some cases, having support components have arelatively large diameter can contribute to the porous support membranehaving relatively beneficial mechanical properties (e.g., relativelyhigh mechanical burst strength). In some embodiments, the porous supportmembrane has a number average support component diameter (e.g., fiberdiameter, cell diameter) of greater than or equal to 10 nm, greater thanor equal to 25 nm, greater than or equal to 50 nm, greater than or equalto 100 nm, greater than or equal to 200 nm, greater than or equal to 500nm, greater than or equal to 1 μm, greater than or equal to 2 μm,greater than or equal to 5 μm, greater than or equal to 10 μm, greaterthan or equal to 20 μm, or more. In some embodiments, the supportcomponents of the porous support membrane are not so large as tocontribute to deleterious effects in the overall anion exchangemembrane, such as insufficient porosity or permeability. In someembodiments, the porous support membrane has a number average supportcomponent diameter (e.g., fiber diameter, cell diameter) of less than orequal to 50 μm, less than or equal to 20 μm, less than or equal to 10μm, less than or equal to 5 μm, less than or equal to 2 μm, less than orequal to 1 μm, less than or equal to 500 nm, less than or equal to 100nm, or less. Combinations of these ranges are possible. For example, insome embodiments, the porous support membrane has a number averagesupport component diameter of greater than or equal to 10 nm and lessthan or equal to 50 μm, greater than or equal to 10 nm and less than orequal to 20 μm, greater than or equal to 100 nm and less than or equalto 1 μm, or greater than or equal to 100 nm and less than or equal to500 nm.

The porous support membrane may comprise any of a variety of suitablematerials (e.g., organic materials, inorganic materials, or combinationsthereof). In some embodiments, the porous support membrane comprises apolymeric material. In some such cases, greater than or equal to 20 wt%, greater than or equal to 30 wt %, greater than or equal to 40 wt %,greater than or equal to 50 wt %, greater than or equal to 60 wt %,greater than or equal to 70 wt %, greater than or equal to 75 wt %,greater than or equal to 80 wt %, greater than or equal to 90 wt %,greater than equal to 95 wt %, or more by weight of the porous supportmembrane is composed of one or more polymers. In some embodiments, lessthan or equal to 100 wt %, less than or equal to 99 wt %, less than orequal to 95 wt %, less than or equal to 90 wt %, less than or equal to80 wt %, less than or equal to 50 wt %, less than or equal to 30 wt %,or less by weight of the porous support membrane is composed of one ormore polymers. Combinations of these ranges are possible. For example,in some embodiments, greater than or equal to 20 wt % and less than orequal to 100 wt %, or greater than or equal to 50 wt % and less than orequal to 99 wt % by weight of the porous support membrane is composed ofone or more polymers. Exemplary polymers that the porous supportmembrane can comprise include, but are not limited to, polyethylene,polyvinyl chloride, polypropylene, polystyrene, polyamide, polyimide,polyacetonitrile, polyvinylacetate, polyethylene glycol, poly etherether ketone, polysulfone, polyacrylamide, polydimethylsiloxane,polyvinylidene fluoride, polyacrylic acid, polyvinyl alcohol,polyphenylene sulfide, polytetrafluoroethylene, cellulose,microfibrillated cellulose, nanofibrillated cellulose, or combinationsor derivatives thereof.

In some embodiments, the porous support membrane comprises a ceramic orglass material. In some such cases, greater than or equal to 20 wt %,greater than or equal to 30 wt %, greater than or equal to 40 wt %,greater than or equal to 50 wt %, greater than or equal to 60 wt %,greater than or equal to 70 wt %, greater than or equal to 75 wt %,greater than or equal to 80 wt %, greater than or equal to 90 wt %,greater than equal to 95 wt %, or more by weight of the porous supportmembrane is composed of one or more ceramic or glass materials. In someembodiments, less than or equal to 100 wt %, less than or equal to 99 wt%, less than or equal to 95 wt %, less than or equal to 90 wt %, lessthan or equal to 80 wt %, less than or equal to 50 wt %, less than orequal to 30 wt %, or less by weight of the porous support membrane iscomposed of one or more one or more ceramic or glass materials.Combinations of these ranges are possible. For example, in someembodiments, greater than or equal to 20 wt % and less than or equal to100 wt %, or greater than or equal to 50 wt % and less than or equal to99 wt % by weight of the porous support membrane is composed of one ormore one or more ceramic or glass materials. Exemplary ceramics that theporous support membrane can comprise include, but are not limited to,borosilicate glass, silica, titania, zirconia, alumina, silicon carbide,silicon nitride, boron nitride, lithium silicate, potassium silicate,tin oxide, iron oxide, or combinations thereof.

In some embodiments, the porous support membrane comprises a metaland/or metal alloy. In some such cases, greater than or equal to 20 wt%, greater than or equal to 30 wt %, greater than or equal to 40 wt %,greater than or equal to 50 wt %, greater than or equal to 60 wt %,greater than or equal to 70 wt %, greater than or equal to 75 wt %,greater than or equal to 80 wt %, greater than or equal to 90 wt %,greater than equal to 95 wt %, or more by weight of the porous supportmembrane is composed of one or more metals and/or metal alloys. In someembodiments, less than or equal to 100 wt %, less than or equal to 99 wt%, less than or equal to 95 wt %, less than or equal to 90 wt %, lessthan or equal to 80 wt %, less than or equal to 50 wt %, less than orequal to 30 wt %, or less by weight of the porous support membrane iscomposed of one or more metals and/or metal alloys. Combinations ofthese ranges are possible. For example, in some embodiments, greaterthan or equal to 20 wt % and less than or equal to 100 wt %, or greaterthan or equal to 50 wt % and less than or equal to 99 wt % by weight ofthe porous support membrane is composed of one or more metals and/ormetal alloys. Exemplary metals that the porous support membrane cancomprise include, but are not limited to, iron, nickel, copper,titanium, aluminum, or combinations thereof. One non-limiting example ofa metal alloys that the porous support membrane can comprise is steel.

In some embodiments, the porous support membrane comprises a combinationof the material described above. For example, in some embodiments, theporous support membrane comprises a combination of a polymeric materialand a ceramic or glass material (or a polymeric material and a metaland/or metal alloy, or a ceramic material and a metal and/or metalalloy). One non-limiting example is an embodiment in which the poroussupport membrane comprises a glass material (e.g. borosilicate glass)containing one or more polymeric materials (e.g., one or more polymericbinders that may enhance mechanical properties of the porous supportmembrane).

In some, but not necessarily all embodiments, the porous supportmembrane comprises one or more amphiphilic molecules on a surface of theporous support membrane. Inclusion of one or more amphiphilic moleculeson a surface of the porous support membrane may, in some cases, promoteenhanced wetting of solutions used during fabrication of the anionexchange membrane. For example, in some cases, the anion exchangemembrane is fabricated via application of a sol-gel solution to theporous support membrane. In some cases, such enhanced wetting maycontribute to a reduction in cracking during certain fabrication steps,such in cases where drying steps are performed. In some such cases,having one or more amphiphilic molecules present on a surface of theporous support membrane may promote wetting of the sol-gel ceramicmaterial on the porous support membrane. In some cases, in amphiphilicmolecule is covalently bound to at least a portion of the porous supportmembrane (e.g., as a surface functional group). In some embodiments, theamphiphilic molecule is coated on or within the porous support membrane(e.g., prior to coating the porous support membrane with the sol-gel).Exemplary amphiphilic molecules include, but are not limited to, sodiumalkyl sulfates (e.g., sodium dodecyl sulfate), dialkyl sulfosuccinate,and alkyltrimethylammonium bromide.

In some embodiments, the porous support membrane has a relatively highsurface area (e.g., prior to being coated with a silica-based ceramic).Having a relatively high surface area of the porous support membranecan, in some cases, promote adhesion between the porous support membraneand the silica-based ceramic. One exemplary way in which a relativelyhigh surface area of the porous support membrane may be achieved is byetching the porous support membrane prior to coating the porous supportmembrane with the silica-based ceramic. The porous support membrane canbe etched, in some cases, with an appropriate solvent, acid, caustic, oroxidizer. In some embodiments, the porous support membrane has aspecific surface area of greater than or equal to 0.0001 m²/g, greaterthan or equal to 0.0002 m²/g, greater than or equal to 0.0005 m²/g,greater than or equal to 0.001 m²/g, greater than or equal to 0.002m²/g, greater than or equal to 0.005 m²/g, greater than or equal to 0.01m²/g, greater than or equal to 0.02 m²/g, greater than or equal to 0.05m²/g, greater than or equal to 0.1 m²/g, greater than or equal to 0.2m²/g, greater than or equal to 0.5 m²/g, or greater prior to beingcoated with a silica-based ceramic. In some embodiments, the poroussupport membrane has a specific surface area of less than or equal to100 m²/g, less than or equal to 50 m²/g, less than or equal to 20 m²/g,less than or equal to 10 m²/g, less than or equal to 5 m²/g, less thanor equal to 2 m²/g, less than or equal to 1 m²/g, or less prior to beingcoated with a silica-based ceramic. Combinations of these ranges arepossible. For example, in some embodiments, the porous support membranehas a specific surface area of greater than or equal to 0.0001 m²/g andless than or equal to 100 m²/g, greater than or equal to 0.001 m²/g andless than or equal to 10 m²/g, or greater than or equal to 0.01 m²/g andless than or equal to 1 m²/g prior to being coated with a silica-basedceramic. The specific surface area of the porous support membrane priorto being coated with the silica-based ceramic can be determined usingBET gas sorption techniques (either before the silica-based ceramiccoating is formed, or by removing the silica-based ceramic from theanion exchange membrane).

In some embodiments, a relatively high percentage of the pore volume ofthe porous support membrane is filled by the silica-based ceramic thatcoats at least a portion of the porous support membrane. The percentageof the pore volume of the porous support membrane filled by thesilica-based ceramic can be determined, for example, using SEM.Generally, several images are taken of both the top and cross-section ofthe anion exchange membrane at various magnifications from 200× for thetop up to 2000× for the cross-section. These images can be compared toimages of the porous support membrane at the same magnifications. Todetermine the extent to which the pore volume of the porous supportmembrane is filled with the silica-based ceramic, the cross-section ofthe anion exchange membrane is inspected. An anion exchange membrane inwhich the pore volume of the porous support membrane is well-filled withthe silica-based ceramic will look dense with little to no obviousmacropores or open areas. In some cases, if there are places that areless dense (e.g., cracks, smaller pores, etc.), it can be beneficial ifthey are not structured in such a way as to create a clear pathway forliquid to travel from one side of the anion exchange membrane to theother. Likewise, in some embodiments, it can be beneficial if the anionexchange membrane is such that images of the top of the membrane looksmooth and uniform. In some embodiments, it is beneficial if themembranes have relatively little surface excess of silica-based ceramic.Surface excess of silica-based ceramic in the anion exchange membranecan be determined by inspecting the SEM for regions of the silica-basedceramic on the top or bottom surface of the porous support membrane. Insome embodiments, the surface excess of silica-based ceramic on top ofthe porous support membrane is less than or equal to 200 μm, less thanor equal to 20 μm, less than or equal to 2 μm, or less, as determined bySEM.

In some embodiments, greater than or equal to 50%, greater than or equalto 60%, greater than or equal to 70%, greater than or equal to 75%,greater than or equal to 80%, greater than or equal to 90%, greater thanor equal to 95%, greater than or equal to 96%, greater than or equal to97%, greater than or equal to 98%, greater than or equal to 99%, greaterthan or equal to 99.9%, and/or up to 100% of the pore volume of theporous support membrane is filled by the silica-based ceramic. In someembodiments, less than or equal to 100%, less than or equal to 99.9%,less than or equal to 99%, less than or equal to 98%, less than or equalto 97%, less than or equal to 96%, less than or equal to 95%, less thanor equal to 90%, less than or equal to 80%, less than or equal to 75%,less than or equal to 70%, or less than or equal to 60% of the porevolume of the porous support membrane is filled by the silica-basedceramic. Combinations of these ranges are possible. For example, in someembodiments, greater than or equal to 50% and less than or equal to100%, greater than or equal to 75% and less than or equal to 100%,greater than or equal to 90% and less than or equal to 100%, or greaterthan or equal to 97% and less than or equal to 100% of the pore volumeof the porous support membrane is filled by the silica-based ceramic, asdetermined by SEM. For example, SEM images can be acquired for arepresentative number of cross-sections (e.g., at least three crosssection) of different regions of the membrane sample. Image processingsoftware (e.g., ImageJ) can then be used to highlight the contrastbetween the void regions (which typically appear black in the images)and filled regions (which typically appear gray in the images) anddivide the area of the void region by the total area probed. So long asyou provide a sufficiently large sample size (˜0.5 cm² in images) youcould determine the total “void area” relative to the total area of thecross-section. It would be important to pull cross-sections frommultiple regions of the membrane to try to get a somewhat representativesample.

The anion exchange membrane may have any suitable thickness. Forexample, referring to FIG. 1A, anion exchange membrane 100 has athickness 154. The thickness of the anion exchange membrane may beselected based on, for example, the application for which the anionexchange membrane is intended or the geometry of a device into which theanion exchange membrane is to be incorporated (e.g., an electrochemicaldevice, a filtration device, etc.). In some embodiments, the anionexchange membrane has a thickness of greater than or equal to 1 μm,greater than or equal to 3 μm, greater than or equal to 5 μm, greaterthan or equal to 10 μm, greater than or equal to 25 μm, greater than orequal to 50 μm, greater than or equal to 100 μm, greater than or equalto 200 μm, greater than or equal to 300 μm, greater than or equal to 400μm, greater than or equal to 500 μm, greater than or equal to 700 μm,greater than or equal to 1,000 μm, greater than or equal to 1,200 μm, ormore. In some embodiments, the anion exchange membrane has a thicknessof less than or equal to 1,500 μm, less than or equal to 1,000 μm, lessthan or equal to 500 μm, less than or equal to 300 μm, less than orequal to 100 μm, less than or equal to 75 μm, less than or equal to 50μm, or less. Combinations of these ranges are possible. For example, insome embodiments, the porous support membrane has a cross-sectionalthickness of greater than or equal to 1 μm and less than or equal to1,500 μm, or greater than or equal to 25 μm and less than or equal to300 μm. The thickness of the porous support membrane in the anionexchange membrane can be determined by taking an SEM cross-section ofthe anion exchange membrane or by using calipers.

In some embodiments, the weight ratio of the silica-based ceramic to theporous support membrane in the anion exchange membrane is greater thanor equal to 1:10, greater than or equal to 1:5, greater than or equal to1:2, greater than or equal to 1:1, greater than or equal to 2:1, greaterthan or equal to 5:1, greater than or equal to 10:1, greater than orequal to 20:1, greater than or equal to 35:1, greater than or equal to50:1, greater than or equal to 75:1, greater than or equal to 100:1, orgreater. In some embodiments, the weight ratio of the silica-basedceramic to the porous support membrane in the anion exchange membrane isless than or equal to 300:1, less than or equal to 250:1, less than orequal to 220:1, less than or equal to 200:1, less than or equal to150:1, less than or equal to 120:1, less than or equal to 100:1, lessthan or equal to 75:1, less than or equal to 50:1, less than or equal to35:1, less than or equal to 20:1, less than or equal to 10:1, less thanor equal to 5:1, less than or equal to 2:1, less than or equal to 1:1,less than or equal to 1:2, less than or equal to 1:5, or less.Combinations of these ranges are possible. For example, in someembodiments, the weight ratio of the silica-based ceramic to the poroussupport membrane in the anion exchange membrane is greater than or equalto 1:10 and less than or equal to 300:1, or greater than or equal to 1:2and less than or equal to 220:1.

In some embodiments, the anion exchange membrane has a density ofgreater than or equal 0.8 g/cm³, greater than or equal 0.9 g/cm³,greater than or equal 1.0 g/cm³, greater than or equal 1.2 g/cm³,greater than or equal 1.5 g/cm³, greater than or equal 1.8 g/cm³, orgreater. In some embodiments, the anion exchange membrane has a densityof less than or equal to 2.2 g/cm³, less than or equal to 2.1 g/cm³,less than or equal to 2.0 g/cm³, less than or equal to 1.9 g/cm³, lessthan or equal to 1.8 g/cm³, less than or equal to 1.7 g/cm³, less thanor equal to 1.6 g/cm³, less than or equal to 1.5 g/cm³, less than orequal to 1.2 g/cm³, or less. Combinations of these ranges are possible.For example, in some embodiments, the anion exchange membrane has adensity of greater than or equal to 0.8 g/cm³ and less than or equal to2.2 g/cm³, or greater than or equal to 1.0 and less than or equal to 2.0g/cm³.

In some embodiments, the anion exchange membrane has a basis weight ofgreater than or equal 320 g/m², greater than or equal 350 g/m², greaterthan or equal to 400 g/m², greater than or equal to 450 g/m², greaterthan or equal to 500 g/m², greater than or equal to 550 g/m², greaterthan or equal to 600 g/m² or greater. In some embodiments, the anionexchange membrane has a basis weight of less than or equal to 880 g/m²,less than or equal to 850 g/m², less than or equal to 800 g/m², lessthan or equal to 750 g/m², less than or equal to 700 g/m², less than orequal to 650 g/m², less than or equal to 600 g/m², less than or equal to550 g/m², less than or equal to 500 g/m², or less. Combinations of theseranges are possible. For example, in some embodiments, the anionexchange membrane has a basis weight of greater than or equal to 320g/m² and less than or equal to 800 g/m². The basis weight can bemeasured, for example, by cutting a 0.1 m² portion of the anion exchangemembrane into 10 samples and measuring the weight of each sample afterdrying at 80° C. in a 0% humidity chamber for 24 hours.

In some embodiments, the anion exchange membrane has a specific surfacearea of greater than or equal 50 m²/g, greater than or equal 75 m²/g,greater than or equal to 100 m²/g, greater than or equal to 150 m²/g,greater than or equal to 200 m²/g, greater than or equal to 300 m²/g,greater than or equal to 400 m²/g, greater than or equal to 500 m²/g, orgreater. In some embodiments, the anion exchange membrane has a specificsurface area of less than or equal to 1,000 m²/g, less than or equal to900 m²/g, less than or equal to 800 m²/g, less than or equal to 750m²/g, less than or equal to 700 m²/g, less than or equal to 650 m²/g,less than or equal to 600 m²/g, less than or equal to 550 m²/g, lessthan or equal 500 m²/g, or less. Combinations of these ranges arepossible. For example, in some embodiments, the anion exchange membranehas a specific surface area of greater than or equal to 500 g/m² andless than or equal to 1,000 g/m².

In some embodiments, the anion exchange membrane comprises acompressible edging material. Such a compressible edging may, in certaincases, serve as a gasket that can seal the membrane. Having acompressible edging material that can serve as a gasket may be useful insome cases in which the anion exchange membrane is incorporated into anelectrochemical device (e.g., a battery, fuel cell, etc.). In somecases, the compressible edging material is mechanically compressible. Insome embodiments, the compressible edging material is resistant to heatand/or harsh chemical environments. FIG. 5 depicts an exemplaryillustration of a non-limiting embodiment in which an anion exchangemembrane 100 comprises an optional compressible edging material 180.

In some embodiments, the anion exchange membrane comprises acompressible edging material along at least a portion of an edge of theanion exchange membrane. In some embodiments, the compressible edgingmaterial infiltrates the porous support membrane by at least 1 μm. Forexample, referring again to FIG. 5, in some embodiments anion exchangemembrane 100 comprises a silica-containing ceramic 150, compressibleedging material 180, and porous support membrane 130 hidden behindsilica-based ceramic 130 and compressible edging material 180, accordingto some embodiments. In some such cases, compressible edging material180 infiltrates porous support membrane 130 by at least 1 μm. In someembodiments, the compressible edging is located along all edges of theanion exchange membrane, defining a gasket (e.g., as shown in FIG. 5).In some embodiments, the compressible edging material covers about 50%or less, 25% or less, 10% or less, or 5% or less of a surface of theanion exchange membrane. In some embodiments, the percentage of theexternal geometrical surface area of the anion exchange membrane notcovered by the compressible edging material is greater than or equal to50%, greater than or equal to 90%, greater than or equal to 95%, ormore. In some embodiments, the percentage of the external geometricsurface area of the anion exchange membrane not covered by thecompressible edging material is greater than or equal to 1 cm², greaterthan or equal to 10 cm², greater than or equal to 100 cm², greater thanor equal to greater than or equal to 1,000 cm² and/or up to 1 m², up to2 m², up to 5 m², up to 10 m², or more. The compressible edging materialmay have a width. For example, compressible edging material 180 in FIG.5 has width 182. In some embodiments, the compressible edging materialis 1 mm or greater in width. In some embodiments the compressible edgingmaterial is 5 mm or greater in width. In some embodiments, the edgeportion is 1 cm or greater in width.

The compressible edging material can be formed on the anion exchangemembrane using any suitable method. For example, in some embodiments,the compressible edging material is formed on the porous supportmembrane prior to forming the silica-based ceramic coating on and/orwithin the porous support membrane. In some cases, the compressibleedging material is formed on the porous support membrane after formingthe silica-based ceramic coating on and/or within the porous supportmembrane.

In some embodiments, forming the compressible edging material includes astep of impregnating an edge portion of the porous support membrane witha polymeric material, for example, impregnating regions at or near oneor more or all edges of the porous support membrane with a compressiblepolymer, sufficient to form a gasket bordering the porous membranesupport membrane (and ultimately the anion exchange membrane). In someembodiments, the compressible edging material is formed using ultrasonicwelding, hot pressing, or UV curing. In some embodiments, impregnatingthe edge portion of the porous support membrane with the compressiblepolymer comprises one or more techniques chosen from melting, solutiondeposition, or in situ reaction.

In some embodiments, the compressible edging material comprises apolymeric material. In some embodiments, the polymeric materialcomprises an elastomeric polymer, such as a thermoplastic elastomericpolymer. Any suitable elastomeric polymer can be used to form thecompressible edging material of the anion exchange membranes disclosedherein. Exemplary polymeric materials that the compressible edgingmaterial can comprise include, but are not limited to silicone, epoxy,polyurethane, acrylic, silicone rubber, poly(styrene-isoprene-styrene),poly(styrene-isobutylene-styrene), polypropylene, polyethylene,polyvinyl chloride, polystyrene, polyamide, polyimide, polyacetonitrile,polyvinylacetate, polyethylene glycol, poly ether ether ketone,polysulfone, polyacrylamide, polydimethylsiloxane, polyvinylidenefluoride, polyacrylic acid, polyvinyl alcohol, polyphenylene sulfide,polytetrafluoroethylene, cellulose, or combinations or derivativesthereof.

As mentioned above, in some cases, inventive features associated withthe anion exchange membrane and materials described herein cancontribute to any of a number of potentially advantageous performancecharacteristics.

In some embodiments, the anion exchange membrane or material (e.g.,anion exchange membrane 100) has a relatively high anion exchangecapacity. Having a relatively high anion exchange capacity is generallyassociated with good performance characteristics for an anion exchangematerial. The anion exchange capacity of a material such as membrane canbe measured using the following procedure. An anion exchange membrane issoaked in an aqueous solution of sodium chloride (2.0 M) for at least 12hours, with the sodium chloride solution being exchanged twice withfresh sodium chloride solution during this 12 hour time period. Aftersoaking in the sodium chloride solution, the membrane is soaked indeionized water for at least 15 minutes, with the deionized water beingexchanged twice with fresh deionized water during this 15 minute timeperiod. After soaking in the deionized water, the membrane is soaked inan aqueous solution containing 1.0 M sodium nitrate for at least 3hours, with the 1.0 M sodium nitrate solution being exchanged twice withfresh 1.0 M sodium nitrate solution (1.0 M sodium nitrate in otherwisedeionized water) during this 3 hour period. The anion exchange membraneis removed from the sodium nitrate solution and rinsed with deionizedwater. All of the sodium nitrate solutions as well as the rinsesolutions are then combined and titrated with an aqueous solutioncontaining 0.010 M silver nitrate using potassium chromate (0.25 M inthe solution) as an indicator. The titration ends when solution changescolor from bright yellow to slightly yellow-brown. An autotitrator canbe used to perform the titration without the use of an indicator such aspotassium chromate, instead using, for example a silver sensing probe. Aset of “blank” sodium nitrate solutions that are not exposed to theanion exchange membrane are used and titrated to determine a baselinechloride ion background for the aqueous solutions. The membrane isrinsed with deionized water and dried in an oven overnight. The weightand of the membrane is recorded following drying step. The anionexchange capacity (AEC) is measured using:

${AEC} = \frac{V_{titrant}C_{titrant}}{w_{dry}}$

where V_(titrant) is the volume of the silver nitrate titrant addedduring the titration, corrected for the baseline chloride concentrationof the aqueous solutions(V_(titrant)=V_(titrant,membrane)−V_(titrant,blanks)), C_(titrant) isthe concentration of the titrant (0.010 M in this case), and w^(dry) isthe weight of the dried membrane in grams. In this disclosure, anionexchange capacity is reported in units of eq/g, which are equivalents(eq) per unit weight (g, grams). The number of equivalents in a solutionrefers to the numbers of moles of an ion (e.g., chloride ions) insolution multiplied by the valence of the ions. The same proceduredescribed above can be used for any anion exchange materials and is notlimited to just membranes.

In some embodiments, it has been observed that anion exchange membranesdescribed herein having a relatively high loading of certain functionalgroups (e.g., quaternary ammonium groups) contributes at least in partto the relatively high anion exchange capacity as compared to certainexisting anion exchange membranes. Additionally, it has been observedthat the anion exchange capacity of anion exchange membranes andmaterials described herein may also depend at least in part on thecomposition of a silicon-containing precursor sol from which asilica-based ceramic of the anion exchange membrane is derived (e.g.,water to silicon ratio, acid strength, ratio of silicon-containingprecursors such as TEOS and TMAPS).

In some embodiments, the anion exchange membrane or material has ananion exchange capacity of greater than or equal to 0.01milliequivalents per gram (meq/g). In some embodiments, the anionexchange membrane or material has an anion exchange capacity of greaterthan or equal to 0.1 meq/g, greater than or equal to 0.2 meq/g, greaterthan or equal to 0.3 meq/g, greater than or equal to 0.5 meq/g, greaterthan or equal to 0.7 meq/g, greater than or equal to 1 meq/g, greaterthan or equal to 1.2 meq/g, greater than or equal to 1.5 meq/g, greaterthan or equal to 1.7 meq/g, or greater. In some embodiments, the anionexchange membrane or material has an anion exchange capacity of lessthan or equal to 2.5 meq/g, less than or equal to 2.2 meq/g, 2 meq/g,less than or equal to 1.8 meq/g, less than or equal to 1.5 meq/g, lessthan or equal to 1.2 meq/g, less than or equal to 1 meq/g, less than orequal to 0.7 meq/g, or less. Combinations of these ranges are possible.For example, in some embodiments, the anion exchange membrane ormaterial has an anion exchange capacity of greater than or equal to 0.01meq/g and less than or equal to 2.5 meq/g, greater than or equal to 0.1meq/g and less than or equal to 2.5 meq/g, greater than or equal to 0.5meq and less than or equal to 2.5 meq/g, or greater than or equal to 1meq/g and less than or equal to 2.5 meq/g. In some embodiments, theanion exchange membrane or material has a relatively high anion exchangecapacity while having a relatively high amount of Si present in thesilica-based ceramic of the anion exchange membrane. For example, insome embodiments, the anion exchange membrane has an anion exchangecapacity of greater than or equal to 0.01 meq/g, greater than or equalto 0.1 meq/g, greater than or equal to 0.2 meq/g, greater than or equalto 0.3 meq/g, greater than or equal to 0.5 meq/g, greater than or equalto 0.7 meq/g, greater than or equal to 1 meq/g and/or up to 1.2 meq/g,up to 1.5 meq/g, up to 1.8 meq/g, or up to 2 meq/g while having Sipresent in the silica-based ceramic in an amount of at least 6 wt %, atleast 10 wt %, at least 12 wt %, at least 15 wt %, at least 17 wt %, atleast 20 wt %, and/or up to 24 wt %, up to 26 wt %, up to 28 wt %, up to30 wt %, up to 40 wt %, up to 47 wt %, up to 60 wt %, or more.

In some embodiments, the anion exchange membrane or material undergoes arelatively small amount of dimensional swelling (in the form of linearexpansion), according to a dimensional swelling test described herein.As mentioned above, having a relatively small amount of dimensionalswelling can, in some cases, be advantageous for an anion exchangemembrane or material. It has been observed that anion exchange membranesand materials described herein, some of which comprise a silica-basedceramic, may undergo relatively less dimensional swelling (e.g., linearexpansion) than certain existing anion exchange membrane or materials,such as those comprising predominantly polymeric components such ashydrocarbon or fluorocarbon polymers. Without wishing to be bound by anyparticular theory, it is believed that linear expansion can occur when amembrane's pore size or structure changes (e.g., swelling, de-swelling)based on the environment of the anion exchange membrane (e.g.,temperature, humidity, salinity). When an anion exchange membrane isincorporated into devices where the edges of the membrane are fixed inplace, for example, an electrochemical device (e.g., an electrochemicalstack), the swelling/de-swelling can result in mechanical stresses thatcan cause membrane failure. Having a relatively low linear expansion canalso make it easier to align membranes (e.g., via making alignment holesin the membrane) when positioning membranes in a device (e.g., a stack)during assembly. However, in some embodiments, it is beneficial to havesome amount of linear expansion (e.g., via swelling) to allow forpercolation of hydrated domains and beneficial performancecharacteristics (e.g., anion exchange capacity, chloride ionconductivity). The linear expansion of an anion exchange membrane can bemeasured using the following dimensional swelling test. The dimensionalswelling test is conducted using a modified version of ASTM D756 andASTM D570. The membrane sample is cut into a 50 mm×50 mm square andconditioned in a room maintained at 23° C. and 50% relative humidity for48 hours. After conditioning, the length and width of the membranesample is measured. The sample is then soaked in either 23° C. water or100° C. water for one hour. After the soaking, the membrane is removedfrom the water and wiped with a dry cloth. Immediately after themembrane is wiped with the cloth, the length of each side is recorded.The linear expansion for a given dimension (e.g., length or width) isdetermined by dividing the measured length of that dimension followingthe step of wiping the membrane with a dry cloth by the original 50 mmlength, and is reported as a percentage change relative to the original50 mm length. For example, a membrane for which a length of 55 mm ismeasured following the soaking and wiping with the cloth has a linearexpansion of 10%, while a membrane for which a length of 60 mm ismeasured following the soaking and wiping with the cloth has a linearexpansion of 20%. The linear expansion of an anion exchange membrane isdetermined by performing the above-mentioned dimensional swelling teston three identical samples and determining the number average of thethree tests.

In some embodiments, the anion exchange membrane has a relatively smalllinear expansion, as mentioned above. In some embodiments, the anionexchange membrane has a linear expansion along at least one dimension ofless than or equal to 10%, less than or equal to 8%, less than or equalto 6%, less than or equal to 5%, less than or equal to 2%, less than orequal to 1%, less than or equal to 0.5%, or less. In some embodiments,the anion exchange membrane has a linear expansion of as low as 0% alongat least one dimension. In some embodiments, the anion exchange membranehas a linear expansion of greater than or equal to 0%, greater than orequal to 0.01%, or greater than or equal to 0.1% along at least onedimension. Combinations of these ranges are possible. For example, insome embodiments, the anion exchange membrane has a linear expansion ofgreater than or equal to 0% and less than or equal to 5%, greater thanor equal to 0% and less than or equal to 2%, greater than or equal to 0%and less than or equal to 1%, or greater than or equal to 0% and lessthan or equal to 0.5% along at least one dimension.

In some embodiments, the anion exchange membrane has a relatively smalllinear expansion while having a relatively large anion exchangecapacity. For example, in some embodiments, the anion exchange membranehas a linear expansion of less than or equal to 20%, less than or equalto 15%, less than or equal to 10%, less than or equal to 8%, less thanor equal to 6%, less than or equal to 5%, less than or equal to 2%, lessor equal to 1%, less than or equal to 0.5%, or less along at least onedimension while having an anion exchange capacity of greater than orequal to 0.01 meq/g, greater than or equal to 0.2 meq/g, greater than orequal to 0.3 meq/g, greater than or equal to 0.5 meq/g, greater than orequal to 0.7 meq/g, greater than or equal to 1 meq/g, and/or up to 1.2meq/g, up to 1.5 meq/g, up to 1.8 meq/g, up to 2 meq/g, up to 2.5 meq/g,or more. Obtaining such high anion exchange capacities while undergoingsuch a small amount of dimensional swelling (e.g., linear expansion)when exposed to water may not be possible with certain existing anionexchange membranes or materials.

In some embodiments, the anion exchange membrane or material has arelatively high anion permselectivity. Anion permselectivity generallyrefers to a metric quantifying an extent to which a membrane or materialis more permeable to anions than cations. Selectivity toward anionsrelative to cations may, in certain applications, be an importantcharacteristic of an anion exchange membrane. Herein, anionpermselectivity is measured by comparing the permeability of themembrane or material to chloride anions as compared to sodium anions.The permselectivity is measured in this case using an open circuitvoltage method. The open circuit voltage method is well known inliterature, being described, for example, in Sata, T., Properties,Characterization and Microstructure of Ion Exchange Membranes. In IonExchange Membranes: Preparation, Characterization, Modification andApplication, Sata, T., Ed. The Royal Society of Chemistry: 2004; pp89-134 and in Kingsbury, R. S.; Flotron, S.; Zhu, S.; Call, D. F.;Coronell, O., Junction Potentials Bias Measurements of Ion ExchangeMembrane Permselectivity. Environmental Science & Technology 2018, 52(8), 4929-4936, both of which are incorporated herein by reference intheir entirety. In the performance of the open circuit voltage methodtests, the membrane is equilibrated in a 0.5 M NaCl aqueous solutionprior to testing. The membrane is then installed in a two-compartmentcell. One compartment of the cell is filled with 100 mL of 0.5 M NaClaqueous solution, while the other compartment is filled with 100 mL of0.1 M NaCl aqueous solution. Each compartment of the two-compartmentcell is stirred, and fresh solution is pumped through each compartmentat a rate of approximately 5 mL/min. AgCl wire electrodes and amultimeter (e.g., Fluke 116 True RMS) is used to make the voltagemeasurements. The AgCl wire electrodes are immersed in the respectivecompartments, and the multimeter is set to the dc voltage setting. Themultimeter probes are connected to the respective AgCl wires, and avoltage reading is taken from the multimeter. The wires are allowed toequilibrate for 30 minutes before the final membrane potential isrecorded. The anion permselectivity is then calculated using the Nernstequation. The offset potential of the AgCl wires is measured in the 0.5M NaCl and 0.1 M NaCl solutions, and averaged to account for thereference potential in the final calculations.

In some embodiments, the anion exchange membrane or material has ananion permselectivity of greater than or equal 65%. In some embodiments,the anion exchange membrane has an anion permselectivity of greater thanor equal to 70%, greater than or equal to 75%, greater than or equal to80%, greater than or equal to 85%, greater than or equal to 90%, greaterthan or equal to 95%, greater than or equal to 97%, greater than orequal to 98%, or higher. In some embodiments, the anion exchangemembrane has an anion permselectivity of less than or equal to 100%,less than or equal to 99%, less than or equal to 98%, less than or equalto 97%, less than or equal to 95%, less than or equal to 90%, less thanor equal to 85%, less than or equal to 80%, or less. Combinations ofthese ranges are possible. For example, in some embodiments, the anionexchange membrane has an anion permselectivity of greater than or equalto 65% and less than or equal to 100%, greater than or equal to 85% andless than or equal to 100%, greater than or equal to 90% and less thanor equal to 100% percent, greater than or equal to 95% and less than orequal to 100%, or greater than or equal to 98% and less than or equal to100%.

In some embodiments, the anion exchange membrane has a relatively highchloride ion (Cl⁻) conductivity (C_(C1)). Chloride ion conductivity canbe a useful metric in evaluating the conductivity of the anion exchangemembrane with respect to anions such as chloride ions. Having arelatively high chloride ion conductivity may be important in certainapplications, such as certain electrochemical applications (e.g.,electrodialysis applications). For example, a relatively high chlorideion conductivity can, in some embodiments, promote energy efficiency inelectrochemical systems. It has been observed that the anion exchangemembranes described herein may have a relatively high chloride ionconductivity at least in part due to inventive characteristics of theanion exchange membranes, such as relatively high loadings of functionalgroups (e.g., quaternary ammonium groups). The chloride ion conductivitymay also be affected by the pore structure of the silica-based ceramic(e.g., pore diameter, pore-pore distance, pore ordering such as fractalaggregate vs. otherwise). It has been observed herein that ionconductivity is not necessarily correlated with other properties of anion exchange membrane or material (e.g., anion exchange capacity), andthat structural and compositional factors leading to relatively highchloride ion conductivity may differ from those affecting otherproperties. For example, if an anion exchange membrane comprisesfunctional groups (e.g., quaternary ammonium groups) localized nearexterior surfaces of the anion exchange membrane, the membrane couldhave a relatively high anion exchange capacity but a poor chloride ionconductivity because the functional groups would not be distributedthrough a thickness of the membrane. In contrast, an anion exchangemembrane with an effective distribution (e.g., a substantiallyhomogeneous distribution) of functional groups may have both arelatively high anion exchange capacity and a relatively high chlorideion conductivity. Factors affecting such a distribution can includechoice of precursor materials (e.g., silicon-containing precursormaterials), ratios of precursor materials (e.g., in a silicon-containingprecursor sol), and choice of porous support membrane (if present).

As another example, certain existing anion exchange compositions havinghigher amounts of functional groups (e.g., quaternary ammonium groups)generally tend to experience greater linear expansion because thefunctional groups tend to adsorb water, leading to swelling. It has beenrealized herein that it is possible to achieve anion exchange membraneshaving relatively high chloride ion conductivity and relatively lowlinear expansion. One way to achieve such a result is by designing apore structure of a silica-based ceramic such that the membrane swellsenough upon hydration to achieve percolated pores, but not so much thatthe pores become too large and lack permselectivity while causingsignificant linear expansion. In some embodiments, percolated poresresulting from some swelling of the membrane can promote both relativelyhigh chloride ion conductivity and relatively high anion exchangecapacity.

The chloride ion conductivity of the anion exchange membrane can bemeasured using the following four-electrode electrical impedancespectroscopy (EIS) procedure. A four-electrode electrical impedancespectroscopy procedure is described in more detail in Galama, A. H.;Hoog, N. A.; Yntema, D. R., Method for determining ion exchange membraneresistance for electrodialysis systems. Desalination 2016, 380, 1-11,which is incorporated herein by reference in its entirety. The membraneis equilibrated in a solution of 0.5 M NaCl prior to testing. Themembrane is then incorporated into a two-compartment cell. Prior toincorporating the membrane into the two compartment cell, thetwo-compartment cell is first assembled and filled with the 0.5 M NaClsolution in order to measure a background resistance of the cell. Thecell is then emptied, reassembled with the membrane and filled with the0.5 NaCl solution, at which point another resistance measurement isacquired. A galvanostatic EIS measurement is used. A constant current of5 mA is applied to working platinum electrodes and is swept from 10,000Hz to 10 Hz with 15 points measured per decade. Ag/AgCl referenceelectrodes are used to measure the resulting voltage across membrane.The resistances for the blank cell and cell with the membraneincorporated are taken from the x-axis intercept of the resultingNyquist plot, indicating the real component of the impedance, and thedifference corresponds to the resistance of the membrane. Theconductance is determined by taking the reciprocal of the resistance,and is normalized to the membrane surface area and thickness todetermine the chloride ion conductivity.

In some embodiments, the anion exchange membrane or material has achloride ion conductivity of greater than or equal to 0.00001 S/cm. Insome embodiments, the anion exchange membrane or material has a chlorideion conductivity of greater than or equal to 0.00005 S/cm, greater thanor equal to 0.0001 S/cm, greater than or equal to 0.0005 S/cm, greaterthan or equal to 0.001 S/cm, greater than or equal to 0.005 S/cm,greater than or equal to 0.01 S/cm, or greater. In some embodiments, theanion exchange membrane or material has a chloride ion conductivity ofless than or equal to 0.3 S/cm, less than or equal to 0.2 S/cm, lessthan or equal to 0.1 S/cm, less than or equal to 0.05 S/cm, less than orequal to 0.02 S/cm, less than or equal to 0.01 S/cm, less than or equalto 0.005 S/cm, less than or equal to 0.001 S/cm, less than or equal to0.0005 S/cm, or less. Combinations of these ranges are possible. Forexample, in some embodiments, the anion exchange membrane or materialhas a chloride ion conductivity of greater than or equal to 0.00001 S/cmand less than or equal to 0.3 S/cm, greater than or equal to 0.001 S/cmand less than or equal to 0.3 S/cm, or greater than or equal to 0.01S/cm and less than or equal to 0.3 S/cm.

In some embodiments, the anion exchange membrane or material has arelatively high chloride ion conductivity and a relatively high anionexchange capacity. For example, in some embodiments, the anion exchangemembrane has a chloride ion conductivity of greater than or equal to0.00001 S/cm, greater than or equal to 0.00005 S/cm, greater than orequal to 0.0001 S/cm, greater than or equal to 0.0005 S/cm, greater thanor equal to 0.001 S/cm, greater than or equal to 0.005 S/cm, greaterthan or equal to 0.01 S/cm, and/or up to 0.02 S/cm, up to 0.05 S/cm, upto 0.1 S/cm, up to 0.2 S/cm, or up to 0.3 S/cm, while having an anionexchange capacity of greater than or equal to 0.01 meq/g, greater thanor equal to 0.1 meq/g, greater than or equal to 0.2 meq/g, greater thanor equal to 0.3 meq/g, greater than or equal to 0.5 meq/g, greater thanor equal to 0.7 meq/g, greater than or equal to 1 meq/g and/or up to 1.2meq/g, up to 1.5 meq/g, up to 1.8 meq/g, or up to 2 meq/g. Combinationsof the above-referenced ranges as well as other ranges of chloride ionconductivity and/or anion exchange capacity described elsewhere hereinare also possible.

In some embodiments, the anion exchange membrane or material has arelatively high chloride ion conductivity and a relatively low linearexpansion. For example, in some embodiments, the anion exchange membranehas a chloride ion conductivity of greater than or equal to 0.00001S/cm, greater than or equal to 0.00005 S/cm, greater than or equal to0.0001 S/cm, greater than or equal to 0.0005 S/cm, greater than or equalto 0.001 S/cm, greater than or equal to 0.005 S/cm, greater than orequal to 0.01 S/cm, and/or up to 0.02 S/cm, up to 0.05 S/cm, up to 0.1S/cm, up to 0.2 S/cm, or up to 0.3 S/cm, while having a linear expansionof less than or equal to 10%, less than or equal to 8%, less than orequal to 6%, less than or equal to 5%, less than or equal to 2%, lessthan or equal to 1%, less than or equal to 0.5%, or less. Combinationsof the above-referenced ranges as well as other ranges of chloride ionconductivity and/or linear expansion described elsewhere herein are alsopossible.

In some embodiments, the anion exchange membrane has a relatively lowosmotic water permeance. The osmotic water permeance of a membranegenerally refers to the flux of water across the membrane due to osmoticpressure. Having a relatively low osmotic water permeance may bebeneficial in certain applications, such as applications where the anionexchange membrane is used in electrochemical applications such aselectrodialysis applications. Details of an exemplary test fordetermining the osmotic water permeance of the membrane are described byKingsbury, Ryan; Zhu, Shan; Flotron, Sophie; Coronell, Orlando (2018):Microstructure determines water and salt permeation in commercial ionexchange membranes. ChemRxiv. Preprint and in Kingsbury, R. S., Zhu, S.,Flotron, S., & Coronell, O. (2018). Microstructure determines water andsalt permeation in commercial ion-exchange membranes. ACS appliedmaterials & interfaces, 10(46), 39745-39756, each of which isincorporated herein by reference in its entirety. The osmotic waterpermeance of the membranes described herein can be determined using thefollowing procedure. The membrane is incorporated into a two-compartmentcell and the volumetric flow rate of water across the membrane ismeasured to determine the flux of water across the membrane due toosmotic pressure. One compartment of the two-compartment cell is filledwith a 4 M NaCl aqueous solution prior to testing. To begin the test,the membrane is assembled into the two-compartment cell and onecompartment of the two-compartment cell is filled with a 2-4 M NaClaqueous solution, and the other compartment of the two-compartment cellis filled with deionized water. Before recording any volume changes, themembrane is left exposed to the concentration gradient between the 2-4 MNaCl solution and the deionized water solution in their respectivecompartments for at least one hour to establish a pseudo-steady state ofwater transported membrane. The cell is then emptied, and fresh 2-4 MNaCl and deionized water are used to refill the cell completely. Thecell is sealed with a lid that is fit with a volumetric syringe that has0.01 mL increments and the levels of the solution in the cell areadjusted to be approximately equal at the start of the test. The twocompartments of the two-compartment cell are agitated via stirring withstir bars for the duration the test. Once the levels are equal, astopwatch is started and the volume changes over time are recorded untilat least 0.05 mL of volume change is observed in each compartment.

Water permeance (A [L·m⁻²·h⁻¹·bar⁻¹]) relates to the hydraulic flux (Jw[L·m⁻²·h⁻¹]) of water across the membrane:

$J_{W} = {{A\left( {{\Delta P} - {\Delta \pi}} \right)} = {\frac{P_{W}}{L}\left( {{\Delta P} - {\Delta \pi}} \right)}}$

where ΔP and Δπ [bar] are the differences in hydraulic and osmoticpressure across the membrane, respectively. The flux, J_(W), can becalculated from the flow rate of water across the membrane (Qw [L·h⁻¹])divided by the membrane area [m²]:

$J_{W} = \frac{Q_{W}}{A}$

The flow rate can be determined by calculating the slope of the volumereadings over time for each compartment and taking the average of thetwo sides (the slopes should be similar in magnitude and opposite insign). Since there is no external hydraulic pressure being applied tothe membranes during the test (ΔP=0), the osmotic pressure is calculatedfrom the composition of the solutions using the Gibbs equation toaccount for the non-ideality of the concentrated solution.

${\Delta \pi} = {{\pi_{c} - \pi_{d}} = {\pi_{c} = {{- \frac{RT}{V_{W}}}{\ln \left( a_{W} \right)}}}}$

The water activity is calculated using the Pitzer activity model via thefreely-available pyEQL software.

In some embodiments, the anion exchange membrane has an osmotic waterpermeance of less than or equal to 100 mL/(hr·bar·m²), less than orequal to 50 mL/(hr·bar·m²). In some embodiments, the anion exchangemembrane has an osmotic water permeance of less than or equal to 45mL/(hr·bar·m²), less than or equal to 40 mL/(hr·bar·m²), less than orequal to 35 mL/(hr·bar·m²), less than or equal to 30 mL/(hr·bar·m²),less than or equal to 20 mL/(hr·bar·m²), less than or equal to 15mL/(hr·bar·m²), less than or equal to 10 mL/(hr·bar·m²), less than orequal to 5, less than or equal to 4, less than or equal to 3, less thanor equal to 2.5, less than or equal to 2 mL/(hr·bar·m²), or less. Insome embodiments, the anion exchange membrane has an osmotic waterpermeance of greater than or equal to 0 mL/(hr·bar·m²), greater than orequal to 0.1 mL/(hr·bar·m²), greater than or equal to 0.2mL/(hr·bar·m²), greater than or equal to 0.3 mL/(hr·bar·m²), greaterthan or equal to 0.5 mL/(hr·bar·m²), greater than or equal to 0.8mL/(hr·bar·m²), greater than or equal to 1 mL/(hr·bar·m²), greater thanor equal to 1.2 mL/(hr·bar·m²), greater than or equal to 1.5mL/(hr·bar·m²), greater than or equal to 2 mL/(hr·bar·m²), greater thanor equal to 5 mL/(hr·bar·m²), or more. Combinations of these ranges arepossible. For example, in some embodiments, the anion exchange membranehas an osmotic water permeance of greater than or equal to 0mL/(hr·bar·m²) and less than or equal to 100 mL/(hr·bar·m²), greaterthan or equal to 0 mL/(hr·bar·m²) and less than or equal to 50mL/(hr·bar·m²), greater than or equal to 0 mL/(hr·bar·m²) and less thanor equal to 10 mL/(hr·bar·m²), greater than or equal to 0 mL/(hr·bar·m²)and less than or equal to 5 mL/(hr·bar·m²), or greater than or equal to0 mL/(hr·bar·m²) and less than or equal to 2 mL/(hr·bar·m²).

In some embodiments, the anion exchange membrane has a relatively largewater uptake. As used herein, the water uptake of the membrane refers tothe amount of water a membrane can absorb when soaked in water at 100°C. The water uptake of the membrane can be measured using the followingprocedure. The membrane is cut into a 50 mm×50 mm square and dried in anoven set to a temperature of greater than 105° C. for 24 hours. Theweight of the membrane is measured after drying. The water uptake isthen measured by immersing the membrane in boiling water at 100° C. forone hour. The membrane is then removed from the boiling water bath andthe surface water is wiped off with a dry cloth. The membrane is thenweighed immediately after the step of wiping the membrane with thecloth. This procedure is performed separately on three identicalmembranes, and the number average for the change in weight of themembrane following the immersion in the boiling water is used todetermine the water uptake of the membrane. It has been unexpectedlyobserved that, in some embodiments, anion exchange membranes describedherein (e.g., anion exchange membranes comprising a silica-based ceramiccomprising covalently bound functional group such as quaternary ammoniumgroups) are capable of relatively high water uptake while undergoing arelatively small amount of dimensional swelling (e.g., linear expansion)compared to certain existing anion exchange membranes. The water uptakecan be represented as a percentage change in weight relative to theweight of the dried membrane.

In some embodiments, the anion exchange membrane has a water uptakegreater than or equal to 1%, greater than or equal to 3%, of greaterthan or equal to 5%, greater than or equal to 8%, greater than or equalto 10%, greater than or equal to 15%, greater than or equal to 20%,greater than or equal to 25%, greater than or equal to 30%, greater thanor equal to 35%, greater than or equal to 40%, greater than or equal to45%, greater than or equal to 50%, greater than or equal to 60%, greaterthan or equal to 70%, or more. In some embodiments, the anion exchangemembrane has water uptake of less than or equal to 100%, less than orequal to 90%, less than or equal to 85%, less than or equal to 80%, lessthan or equal to 75%, less than or equal to 70%, less than or equal to65%, less than or equal to 60%, less than or equal to 50%, less than orequal to 40%, less than or equal to 35%, less than or equal to 25%, lessthan or equal to 15%, less than or equal to 10%, or less. Combinationsof these ranges are possible. For example, in some embodiments, theanion exchange membrane has a water uptake of greater than or equal to1% and less than or equal to 100%, greater than or equal to 5% and lessthan or equal to 50%, or greater than or equal to 10% and less than orequal to 25%.

In some embodiments, the anion exchange membrane has a relatively highwater uptake and a relatively low linear expansion. In some embodiments,the anion exchange membrane has a water uptake of greater than or equalto 1%, greater than or equal to 3%, of greater than or equal to 5%,greater than or equal to 8%, greater than or equal to 10%, greater thanor equal to 15%, greater than or equal to 20%, greater than or equal to25%, greater than or equal to 30%, greater than or equal to 35%, greaterthan or equal to 40%, greater than or equal to 45%, greater than orequal to 50%, or greater than or equal to 60%, greater than or equal to70%, while having a linear expansion of less than or equal to 10%, lessthan or equal to 8%, less than or equal to 6%, less than or equal to 5%,less than or equal to 2%, less than or equal to 1%, less than or equalto 0.5%, or less. Combinations of the above-referenced ranges as well asother ranges of water uptake and/or linear expansion described elsewhereherein are also possible.

In some embodiments, the anion exchange membrane has a relatively highmechanical burst pressure. Mechanical burst pressure of a membranegenerally refers to the amount of force that can be applied to themembrane prior to the membrane undergoing mechanical failure andbursting. Having a relatively high mechanical burst pressure can, insome instances, be advantageous for an anion exchange membrane. Forexample, in certain applications involving flowing solutions in contactwith the anion exchange membrane (e.g., redox flow batteries) orapplying a hydrostatic or hydraulic pressure to the anion exchangemembrane (e.g., reverse osmosis or nanofiltration), having a sufficientmechanical burst pressure can be important in avoiding failure of themembrane during operation. It has been observed that, in someembodiments, the anion exchange membranes described herein can possessgood mechanical properties such as a high mechanical burst pressurewhile also possessing good performance characteristics (e.g., anionexchange capacity, anion permselectivity). In certain cases, such acombination of good mechanical properties and good performancecharacteristics can be achieved by combining the silica-based ceramic(which may impart good anion exchange performance characteristics) withthe porous support membrane (which may impart good mechanicalperformance).

The mechanical burst pressure of the anion exchange membrane can bedetermined using the following procedure. The procedure can be used todetermine a burst pressure in units of Newtons (N). The procedure iscarried out based on a modified version of ASTM D6797. A membrane havinga circular shape with a diameter of 70 mm is kept hydrated in waterprior to testing. The membrane is removed from the water, and excesswater on the surface of the membrane is wiped off with a dry cloth.After the step of wiping the membrane with a dry cloth, the membrane isclamped in a fixture with a ring clamp having an internal diameter of 40mm in the center of the membrane. A polished steel ball having adiameter 25 mm is used to apply a force to the membrane. The polishedsteel ball is attached to the movable part of a tensile test machine ofthe constant rate of extension type. The tensile test machine is startedby setting the moving rate to 305 mm/minute, and ball movement ismaintained until the membrane bursts.

As mentioned above, in some embodiments, the anion exchange membrane hasa relatively high mechanical burst pressure, as measured using theprocedure described above. In some embodiments, the anion exchangemembrane has a mechanical burst pressure of at least 1.5 N, at least 1.7N, at least 2.0 N, at least 5 N, at least 10 N, at least 25 N, or more.In some embodiments, the anion exchange membrane has a mechanical burstpressure of less than or equal to 1,000 N, less than or equal to 900 N,less than or equal to 800 N, less than or equal to 700 N, less than orequal to 600 N, less than or equal to 500 N, less than or equal to 400N, less than or equal to 250 N, less than or equal to 100 N, less thanor equal to 75 N, less than or equal to 50 N, less than or equal to 25N, or less. Combinations of these ranges are possible. For example, insome embodiments, the anion exchange membrane has a mechanical burstpressure of at least 1.5 N and less than or equal to 1,000 N, or greaterthan or equal to 1.7 N and less than or equal to 400 N.

The mechanical burst pressure of the anion exchange membrane can also bedetermined in units of pressure. Such units provide a measure that isindependent of dimensional properties of the anion exchange membrane(e.g., membrane area). The mechanical burst pressure of the anionexchange membrane can be determined in units of pressure using thefollowing procedure. The procedure is carried out based on a modifiedversion of ASTM D3786 using a Cyeeyo 302AQT burst tester. A membranehaving a circular shape with a diameter of 40 mm is kept hydrated inwater prior to testing. The membrane is removed from the water, andexcess water on the surface of the membrane is wiped off with a drycloth. After the step of wiping the membrane with a dry cloth, themembrane is clamped in a fixture with a ring clamp having an internaldiameter of 33 mm in the center of the membrane. During the test, thediaphragm of the burst tester below the sample is expanded upwards untilthe point of specimen rupture. The burst point, indicated as the peakpressure value, can be read from display of the burst test. The burstpoint corresponds to the mechanical burst pressure.

As mentioned above, in some embodiments, the anion exchange membrane hasa relatively high mechanical burst pressure, as measured in units ofpressure using the procedure described above. In some embodiments, theanion exchange membrane has a mechanical burst pressure of at least 2.0pounds per square inch (PSI), at least 2.1 PSI, at least 2.5 PSI, atleast 3.0 PSI, at least 3.5 PSI, at least 4.0 PSI, at least 5.0 PSI, atleast 6.0 PSI, at least 8.0 PSI, at least 10.0 PSI, at least 12.0 PSI,at least 15.0 PSI, at least 20.0 PSI, at least 25.0 PSI, at least 30.0PSI, at least 40.0 PSI, at least 50.0 PSI, at least 60.0 PSI at least75.0 PSI, at least 100.0 PSI, or more. In some embodiments, the anionexchange membrane has a mechanical burst pressure of less than or equalto 1,000 PSI, less than or equal to 900 PSI, less than or equal to 800PSI, less than or equal to 700 PSI, less than or equal to 600 PSI, lessthan or equal to 500 PSI, less than or equal to 400 PSI, less than orequal to 250 PSI, less than or equal to 150 PSI, less than or equal to100 PSI, less than or equal to 90 PSI, less than or equal to 80 PSI,less than or equal to 75 PSI, less than or equal to 70 PSI, less than orequal to 65 PSI, less than or equal to 60 PSI, less than or equal to 55PSI, less than or equal to 50 PSI, less than or equal to 40 PSI, lessthan or equal to 30 PSI, less than or equal to 25 PS, less than or equalto 10 PSI or less. Combinations of these ranges are possible. Forexample, in some embodiments, the anion exchange membrane has amechanical burst pressure of at least 2.0 PSI and less than or equal to1,000 PSI, greater than or equal to 5.0 PSI and less than or equal to400 PSI, or greater than or equal to 20 PSI and less than or equal to 60PSI.

In certain aspects, methods of fabricating the anion exchange membranesin materials described herein are provided. One exemplary method offabricating the anion exchange membrane involves a sol-gel process.

FIG. 6 is a flow diagram illustrating one non-limiting method offabricating an anion exchange membrane. In some embodiments, a poroussupport membrane, as described herein, is provided. For example, FIG. 6shows a porous support membrane 130. In some cases, an optional step ofapplying a compressible edging material to the porous support membraneis performed. For example, as shown in step 1 in FIG. 6, a compressibleedging material 180 is formed on porous support membrane 130.

In a non-limiting case, the optional compressible edging material isformed at least in part by adding a polymer to the top surface of theporous support membrane such that the polymer infiltrates the entirethickness of the porous support membrane and forms a border having awidth of at least 1 μm around the edge region of the porous supportmembrane. Such a compressible edging material may, in some cases, act asa gasket capable of contributing to sealing the anion exchange membrane(e.g., in a cell). The method of forming the compressible edge materialdepends on the composition (e.g., polymeric material) used to form thecompressible edging material. In some cases, the compressible edgingmaterial can be applied as a film and/or sheet using heating, solvent,or radiation. In some embodiments, the optional compressible edgingmaterial can be applied to the porous support membrane from a liquidphase as a solution or dispersion using any of a variety of knowncoating techniques (e.g., dip, spray, drop, blade, screen, etc.). Insome embodiments, the method of forming the compressible edging materialcan include a step of performing an in situ reaction after deposition ofthe precursor material. For example, in some cases, an in situ reactiontakes place in which deposited monomeric units react to form a polymerwithin the porous support membrane. In some embodiments, the percentageof the external geometrical surface area of the porous support membranenot covered by the compressible edging material is greater than or equalto 30%, greater than or equal to 40%, greater than or equal to 50%,greater than or equal to 70%, greater than or equal to 80%, greater thanor equal to 90%, greater than or equal to 95%, greater than or equal to99% or more. In some embodiments, the area of the external geometricsurface area of the porous support membrane not covered by thecompressible edging material is greater than or equal to 1 cm², greaterthan or equal to 10 cm², greater than or equal to 100 cm², greater thanor equal to greater than or equal to 1,000 cm² and/or up to 1 m², up to2 m², up to 5 m² 10 m², or more.

In some embodiments, a silicon-containing precursor sol is applied tothe porous support membrane during the fabrication of the anion exchangemembrane. For example, referring again to FIG. 6, in step 2, asilicon-containing precursor sol is applied to porous support membrane130 (optionally comprising compressibility material 180) via solution270. Exemplary compositions of the silicon-containing precursor sol aredescribed herein. In some embodiments, the silicon-containing precursorsol is applied to the porous support membrane such that thesilicon-containing precursor sol wicks into the porous support membraneand coats at least a portion of the porous support membrane. In someembodiments, the sol wicks into the interior of the porous supportmembrane and in some cases fills some or all of the porous volume of theporous support membrane. The silicon-containing precursor sol (e.g.,solution 270) can be applied to the porous support membrane using one ormore standard coating processes such as dip coating, spray coating, rollcoating, blade coating, screen printing, or blowing with air (e.g., withan air knife) according to some embodiments. Excess silicon-containingprecursor sol can be removed via any suitable method, such as scraping.The porous support membrane can be in any of a variety of orientations(e.g., vertical, horizontal) during the step of applying thesilicon-containing precursor sol to the porous support membrane. In someembodiments, the silicon-containing precursor sol can be applied to theporous support membrane when the porous support membrane is flat andfree standing. In some embodiments, the silicon-containing precursor solcan be applied to the porous support membrane when the porous supportmembrane is flat and contacting another surface. In some embodiments,the silicon-containing precursor sol can be applied to the poroussupport membrane when the porous support membrane is curved and freestanding. In some embodiments, the silicon-containing precursor sol canbe applied to the porous support membrane when the porous supportmembrane is curved and contacting another surface. As one example, insome cases, the porous support membrane can be arranged to be in acylindrical or conical shape during the application of thesilicon-containing precursor sol (e.g., solution 270 in FIG. 6). In someembodiments, the silicon-containing precursor sol can be applied to theporous support membrane when the membrane is held taut in at least onedimension.

In some embodiments, the silicon-containing precursor sol is a singlephase sol prior to and/or during the step of applying thesilicon-containing precursor sol to the porous support membrane. Forexample, in embodiments in which the silicon-containing precursor solcomprises two or more different types of silicon-based precursors (e.g.,both a silane comprising a functional group such as a quaternaryammonium group and a silane that does not comprise such a functionalgroup), the silicon-containing precursor sol is a homogeneous mixturecomprising the two or more different types of silicon-based precursors.Applying a single phase sol can, in some cases, allow for the formationof a coating of the silica-based ceramic on the porous support membranehaving a number of desirable properties, such as relatively high loadingand/or substantially homogeneous distribution of functional groups(e.g., quaternary ammonium groups) in the coating.

In some embodiments, the silicon-containing precursor sol (e.g.,solution 270 in FIG. 6) is aged prior to the step of applying thesilicon-containing precursor sol to the porous support membrane. In someembodiments, the aging can occur for at least zero minutes, at least 30minutes, at least two hours, or more, from the time the precursormaterials are mixed together to form the sol. In some embodiments, theaging can occur for less than or equal to one week, less than or equalto 48 hours, less than or equal to 24 hours, or less. Combinations ofthese ranges are possible. For example, in some embodiments, the agingcan occur for at least 0 minutes and less than or equal to one week,greater than or equal to 30 minutes and less than or equal to 48 hours,or greater than or equal to two hours and less than or equal to 24hours. In some embodiments, the temperature of the silicon-containingprecursor sol during the aging is at least 0° C., at least 20° C., atleast 30° C., or more. In some embodiments, the temperature of thesilicon-containing precursor sol during the aging is less than or equalto 80° C., less than or equal to 60° C., less than or equal to 50° C.,or less. Combinations of these ranges are possible. For example, in someembodiments, the temperature of the silicon-containing precursor solduring aging is at least 0° C. and less than or equal to 80° C., atleast 20° C. and less than or equal to 60° C., or at least 30° C. andless than or equal to 50° C. In some cases, silicon-containing precursorsol is aged in an open atmosphere (e.g., open to ambient air), while insome embodiments the converting step is performed in a sealed atmosphere(e.g., in atmosphere fluidically isolated from ambient air). Aging in anopen atmosphere can allow for at least partial evaporation during aging,which may be desirable in some but not necessarily all embodiments.Aging in an sealed atmosphere reduce or eliminate evaporation duringaging, which may be desirable in some but not necessarily allembodiments.

In some embodiments, the porous support membrane, now comprising atleast a portion of the silicon-containing precursor sol, is removed fromthe solution used to apply the silicon-containing precursor sol, and astep of converting the silicon-containing precursor sol to thesilica-based ceramic is performed. For example, now referring to step 3in FIG. 6, porous support membrane 130, at least a portion of which isnow coated with at least a portion of the silicon-containing precursorsol of solution 270, is removed from solution 270. Thesilicon-containing precursor sol coated on and/or within at least aportion of the porous support membrane (e.g., coated membrane 280) isthen converted to the silica-based ceramic, according to someembodiments. In some embodiments, converting the silicon-containingprecursor sol to the silica-based ceramic comprises performing ahydrolysis and condensation reaction. It has been observed in thecontext of the present disclosure that, in some such embodiments, thehydrolysis and condensation reaction results in a self-assembly ofcomponents of the silicon-containing precursor sol to form thesilica-based ceramic (e.g., as an interconnected network structure that,in some cases, is nanoporous).

In some embodiments, the step of converting the silicon-containingprecursor sol coating at least a portion of the porous support membraneinto the silica-based ceramic (e.g., via a hydrolysis and condensationreaction) proceeds for at least one second, at least 1 minute, at least30 minutes, at least 1 hour, at least 2 hours, at least 4 hours, ormore. In some embodiments, the step of converting the silicon-containingprecursor sol coating at least a portion of the porous support membraneinto the silica-based ceramic proceeds for less than or equal to 2weeks, less than or equal to 1 week, less than or equal to 96 hours,less than or equal to 48 hours, less than or equal to 24 hours, or less.Combinations of these ranges are possible. For example, in someembodiments, the step of converting proceeds for at least 1 second andless than or equal to 2 weeks, at least 2 hours and less than or equalto 48 hours, or at least 4 hours and less than or equal to 24 hours. Thestep of converting the silicon-containing precursor sol coating at leasta portion of the porous support membrane into the silica-based ceramic(e.g., via a hydrolysis and condensation reaction) can be performed inany of a variety of conditions. In some cases, the converting step isperformed in an open atmosphere (e.g., open to ambient air), while insome embodiments the converting step is performed in a sealed atmosphere(e.g., in atmosphere fluidically isolated from ambient air). In someembodiments, the converting step is performed in an atmosphere having ahumidity of at least 0% and up to 100% humidity.

The step of converting the silicon-containing precursor sol coating atleast a portion of the porous support membrane into the silica-basedceramic (e.g., via a hydrolysis and condensation reaction) may beperformed at any of a variety of temperatures, depending on thecomposition of the silicon-containing precursor sol and the desiredproperties of the anion exchange membrane. In some embodiments, theconverting step occurs at room temperature or cooler, while in someembodiments, the converting step occurs at elevated temperatures. Insome such cases, the coated porous support membrane is kept in a dryer(e.g., an oven) during the converting step. For example, FIG. 6 shows anexemplary coated porous support 20 optionally being kept in a dryer 24during at least a portion of step 3, according to some embodiments. Insome embodiments, the converting step is performed with the coatedporous support membrane kept in an environment having a temperature ofgreater than or equal to 0° C., greater than or equal to 20° C., orhigher. In some embodiments, the converting step is performed with thecoated porous support membrane being kept in an environment having atemperature of less than or equal to 150° C., less than or equal to 80°C., less than or equal to 60° C., or less. Combinations of these rangesare possible. For example, in some embodiments, the converting step isperformed with the coated porous support membrane kept in an environmenthaving a temperature of greater than or equal to 0° C. and less than orequal to 150° C., greater than or equal to 0° C. and less than or equalto 80° C., or greater than or equal to 20° C. and less than or equal to60° C. The temperature of the conditions under which the converting step(e.g., hydrolysis and condensation of the silicon-containing precursorsol to form the silica-based ceramic) occurs may be relatively lowcompared to certain existing techniques for forming ceramics, such ashigh-temperature sintering and calcination. In some cases, the use ofrelatively low temperatures to form the silica-based ceramic allows forthe costs and resources needed to fabricate the anion exchange membraneto be reduced compared to certain existing techniques.

In some embodiments, the converting step can be performed while thecoated porous support membrane is positioned on, or in contact with, asurface. For example, in some embodiments, the converting step can beperformed while the coated porous support membrane is positioned on arelatively flat surface, or relatively flat and porous surface. However,it should be understood that the coated porous support membrane need notbe positioned on or in contact with the surface during the convertingstep. In some embodiments, the coated porous support membrane ispositioned with a horizontal orientation with respect to a surface(e.g., a horizontal orientation with respect to a surface of an oven),while in some embodiments, the coated porous support membrane ispositioned with a vertical orientation with respect to a surface (e.g.,a vertical orientation with respect to a surface of an oven).

In some embodiments, the converting step can optionally be terminated toconclude step 3. For example, in some embodiments, the reaction takingplace during the converting step (e.g., the hydrolysis and condensationreaction) can be quenched by applying an aqueous solution. The aqueoussolution can be applied using standard coating processes such as dip,spray, blade, screen printing. For example, in some embodiments,quenching the reaction comprises contacting the converted coated poroussupport membrane with an aqueous solution (e.g., via application of theaqueous solution to the converted coated porous support membrane, viasubmersion of the coated porous support membrane within the aqueoussolution, etc.). In some embodiments, the aqueous solution used toquench the reaction has a pH of greater than or equal to −1, greaterthan or equal to zero, greater than or equal to 1, greater than or equalto 2, greater than or equal to 3, greater than or equal to 4, greaterthan or equal to 5, greater than equal to 6, greater than or equal to 7,greater than or equal to 8, greater than or equal to 9, greater than orequal to 10, or greater. In some embodiments, the aqueous solution usedto quench the reaction has a pH of less than or equal to 14, less thanor equal to 13, less than or equal to 12, less than or equal to 11, lessthan or equal to 10, less than or equal to nine, less than or equal to8, less than or equal to 7, less than or equal to 6, less than or equalto 5, less than or equal to 4, less than or equal to 3, or less.Combinations of these ranges are possible. For example, in someembodiments, the aqueous solution used to quench the reaction has a pHof greater than or equal to −1 and less than or equal to 14, greaterthan or equal to −1 and less than or equal to 7, greater than or equalto 5 and less than or equal to 7.

In some instances, it is desirable to remove excess silica-based ceramicon the anion exchange membrane (e.g., to reduce or eliminate surfaceexcess). Excess silica-based ceramic can be removed using any of avariety of suitable methods. Exemplary methods include, but are notlimited to, removal via mechanical squeegee, removal via air knife,and/or removal via heating (e.g., to an elevated temperature).

In some embodiments, the method for fabricating the anion exchangemembrane described herein is completed following step 3 described above.For example, in some embodiments, a membrane 282 produced following step3 is a fully fabricated anion exchange membrane (e.g., anion exchangemembrane 150 described herein). In some cases, steps of the methoddescribed above can be repeated. For example, in some embodiments, step2 and step 3 of the fabrication method can be repeated. Repeating steps2 and 3 can, in some cases, result in increased coating on and/or withthe porous support membrane with the silica-based ceramic. For example,repeating steps 2 and 3 may allow for the silicon-containing precursorsol to infiltrate regions of the porous support membrane that were notinfiltrated by the silicon-containing precursor sol during previousperformances of step 2. Such repetitions of steps 2 and 3 may, in somecases, result in up to 100% filling of the porous support membrane bythe silica-based ceramic. It should be understood, however, thatrepeating steps 2 and 3 above too many times may, in some cases, cause abuildup of surface excess of silica-based ceramic on the porous supportmembrane. In other words, in some cases, a layer of silica-based ceramichaving too large a thickness may result on the exterior surface of theanion exchange membrane, which in some cases may be detrimental to theperformance of the anion exchange membrane in certain applications. Ithas been observed that, in some cases, performing steps 2 and 3described above a total of between 1-3 times may result in anionexchange membranes having beneficial performance characteristics. It hasbeen observed that, in some cases, performing steps 2 and 3 describedabove a total of between 1-6 times (e.g., 4-6 times) may result in anionexchange membranes having beneficial performance characteristics.

As mentioned above, in some embodiments, a fully-fabricated anionexchange membrane can be prepared upon the completion of step 3 asdescribed above and shown in FIG. 6. For example, in some embodiments inwhich the silicon-containing precursor sol includes a componentcomprising a functional group (e.g., a silane comprising a quaternaryammonium group) that is desirable to be in the finished anion exchangemembrane, that functional group may be present in the anion exchangemembrane produced following step 3, thereby making the anion exchangemembrane produced upon the completion of step 3 suitable for certainapplications without further modification. As one non-limiting example,in some embodiments in which the silicon-containing precursor solcomprises a tetraalkylorthosilicate (e.g., TEOS) and atrialkoxysilylalkyl-N,N,N-trialkylammonium ((e.g.,trimethoxysilylpropyl-N,N,N-trimethylammonium, TMAPS) as precursors, nofurther modification of the anion exchange membrane following thecompletion of step three may be necessary, at least because the anionexchange membrane at this stage comprises quaternary ammonium groups.

However, in some embodiments, one or more additional steps may beperformed following step 3 of the methods described herein. For example,in some embodiments, the porous support membrane coated with thesilica-based ceramic does not comprise functional groups (e.g.,quaternary ammonium groups) that are desired to be present in thecompleted anion exchange membrane following step 3. For example, in someembodiments, the silicon-containing precursor sol used to coat theporous support membrane does not comprise a component comprising thedesired functional group. As one non-limiting example, in someembodiments the silicon-containing precursor sol comprises atetraalkylorthosilicate (e.g., TEOS) and a silane comprising a moietycomprising a leaving group (e.g., a halo group, a tosylate group, atrifluoromethane group) as precursors. In some such cases, furtherchemical reactions may need to be performed to convert the moietycomprising a leaving group to a desired quaternary ammonium group (e.g.,via a nucleophilic substitution). As such, in some cases, furtherchemical reactions may be performed to form the desired functionalgroups.

In some embodiments, an optional step of exposing the coated poroussupport membrane following step 3 to water may be performed. Forexample, as shown in FIG. 6, an optional step 4 in which membrane 282 iscontacted with water can be performed. Exposing the coated poroussupport membrane following step 3 to water may, in some embodiments,result in the removal of certain components that may be undesirable infollow-up steps of the fabrication process. For example, in someembodiments, exposing the coated porous support membrane to water mayremove acid from the membrane structure. Water can be applied using oneor more standard coating processes such as dip, spray, blade, and screenprinting.

In some embodiments, a method for forming the anion exchange membranecomprises a step of exposing a porous support membrane, at least aportion of which is coated with the silica-based ceramic comprising an amoiety comprising a leaving group, to an amine. As shown in FIG. 6, insome embodiments, membrane 282 comprises a porous support membranecoated with a silica-based ceramic comprising a moiety comprising aleaving group, and membrane 282 is exposed to an amine in solution 272during optional step 5. In some embodiments, the method further reactingthe amine with the moiety to release the leaving group and form aquaternary ammonium group covalently bound to the silica-based ceramic.In some such cases, the steps of exposing the porous support membrane tothe amine and reacting the moiety with the amine to form a quaternaryammonium group results in the anion exchange membrane comprising aquaternary ammonium group (e.g., covalently bound to the silica-basedceramic).

In some embodiments, the silica-based ceramic comprising the moietycomprising the leaving group comprises a relatively high percentage ofsilicon. For example, in some embodiments, the silica-based ceramiccomprises Si in an amount greater than or equal to 6 wt %, greater thanor equal to 10 wt %, greater than equal to 12 wt %, greater than orequal to 15 wt %, greater than or equal to 17 wt %, greater than orequal to 20 wt %, greater than or equal to 24 wt %, greater than orequal to 30 wt %, greater than or equal to 40 wt %, greater than orequal to 60 wt %, or more in the silica-based ceramic. In someembodiments, the silica-based ceramic comprises Si in an amount lessthan or equal to 60 wt %, less than or equal to 50 wt %, less than orequal to 47 wt %, less than or equal to 40 wt %, less than or equal to30 wt %, less than or equal to 28 wt %, less than or equal to 26 wt %,less than or equal to 24 wt %, less than or equal to 22 wt %, less thanor equal to 20 wt %, less than or equal to 17 wt %, or less in thesilica-based ceramic. Combinations of these ranges are possible. Forexample, in some embodiments, the silica-based ceramic comprises Si inan amount greater than or equal to 6 wt % and less than or equal to 60wt %, or greater than or equal to 17 wt % and less than or equal to 26wt % in the silica-based ceramic.

The moiety comprising the leaving group may be any functional groupthat, upon a nucleophilic substitution step, can release a leaving groupto form a quaternary ammonium group. For example, in some embodiments,the moiety comprising the leaving group is substituted alkyl group(e.g., a haloalkyl group such as a chloropropyl group.

The amine may be any amine suitable to react with the moiety comprisingthe leaving group to form a quaternary ammonium group. In someembodiments, the amine is a tertiary amine. In some embodiments, theamine is trimethylamine.

Exposing the porous support membrane, coated with the silica-basedceramic comprising a moiety comprising the leaving group, to the amineagent may comprise the step of applying the amine to the coated membranein any of a variety of suitable ways. For example, as mentioned above,in some embodiments, the exposing step comprises exposing the coatedporous support membrane to a solution containing the amine (e.g.,solution 272 in FIG. 6). The amine can be applied to the coated poroussupport membrane, in some cases, using standard coating processes, suchas dip coating, spray coating, roll coating, blade coating, or screenprinting. In some embodiments, the amine (e.g., trimethylamine) may beapplied to the coated porous support membrane by applying (e.g., viadipping) a solution comprising at least 1 vol %, at least 5 vol %, atleast 10 vol %, at least 15 vol %, at least 20 vol %, or more amine(e.g., triethylamine). In some embodiments, the amine (e.g.,trimethylamine) may be applied to the coated porous support membrane byapplying (e.g., via dipping) an solution comprising less than or equalto 50 vol %, less than or equal to 40 vol %, less than or equal to 30vol %, less than or equal to 25 vol %, less than or equal to 20 vol %,less than or equal to 15 vol %, less than or equal to 10 vol %, or less,amine (e.g., trimethylamine). Combinations of these ranges are possible.For example, in some embodiments, an amine may be applied to the coatedporous support membrane by applying an solution comprising greater thanor equal to 1 vol % and less than or equal to 50 vol %, greater than orequal to 10 vol % and less than or equal to 50 vol %, or greater than orequal to 20 vol % and less than or equal to 50 vol % of amine (e.g.,trimethylamine).

In some embodiments, the step of reacting the moiety comprising theleaving with the amine to form quaternary ammonium group is performedusing a solution comprising the amine that is kept at a suitabletemperature. For example, in some embodiments, a solution comprising theamine used for the reaction has a temperature of greater than or equalto 0° C., greater than or equal to 20° C., or more. In some embodiments,the solution comprising the amine used for the reaction has atemperature of less than or equal to 100° C., less than or equal to 60°C., less than or equal to 50° C., or less. Combinations of these rangesare possible. For example, in some embodiments, the solution comprisingthe solution comprising the amine used for the reaction has atemperature of greater than or equal to 0° C. and less than or equal to100° C., greater than or equal to 0° C. and less than or equal to 60°C., or greater than or equal to 20° C. and less than or equal to 50° C.The duration of the oxidation reaction that converts the moietycomprising the leaving group to a quaternary ammonium group may dependon the reaction kinetics as well as, for example, the concentration ofleaving groups (e.g., halo groups such as chloro groups) on or withinthe coated porous support comprising the silica-based ceramic. In somecases, the reaction may proceed for at least 1 minute, at least 30minutes, at least 1 hour, or more. In some cases, the reaction mayproceed for less than or equal to 1 week, less than or equal to 48hours, less than or equal to 24 hours, or less. Combinations of theseranges are possible. For example, in some embodiments, the reaction mayproceed for greater than or equal to 1 minute and less than or equal to1 week, greater than or equal to 30 minutes in less than or equal to 48hours, or greater than or equal to 1 hour and less than or equal to 24hours.

In some embodiments, an optional drying step can be performed on theanion exchange membrane following the reaction of the amine and themoiety comprising the leaving group to form a quaternary ammonium group.FIG. 6 shows optional step 6, where a reacted membrane 284 comprisingquaternary ammonium groups is dried by being kept in an optional dryer26, according to some embodiments. It should be understood however, thatin some embodiments, the drying step can be performed without keepingthe reacted anion exchange membrane in a dryer. In some embodiments, thestep of drying the reacted anion exchange membrane comprising aquaternary ammonium group proceeds for at least 1 second, at least 1minute, at least 30 minutes, at least 1 hour, at least 2 hours, at least4 hours, or more. In some embodiments, the step of drying the reactedanion exchange membrane comprising a quaternary ammonium group proceedsfor up to 24 hours, up to 2 days, up to one week, up to 2 weeks, ormore. Combinations of these ranges are possible. For example, in someembodiments, the step of drying the reacted anion exchange membranecomprising a quaternary ammonium group proceeds for at least 1 secondand up to 2 weeks, at least 2 hours and up to 2 days, or at least 4hours and up to 24 hours. The step of drying the reacted anion exchangemembrane comprising a quaternary ammonium group can be performing in anyof a variety of conditions. In some cases, the drying step is performedin an open atmosphere (e.g., open to ambient air), while in someembodiments the drying step is performed in a sealed atmosphere (e.g.,in atmosphere fluidically isolated from ambient air). In someembodiments, the drying step is performed in an atmosphere having ahumidity of at least 0% and up to 100% humidity.

The step of drying the reacted anion exchange membrane comprising aquaternary ammonium group may be performed at any of a variety oftemperatures. In some embodiments, the drying step occurs at roomtemperature or cooler, while in some embodiments, the drying step occursat elevated temperatures. In some embodiments, the drying step isperformed with the reacted anion exchange membrane kept in anenvironment having a temperature of greater than or equal to 0° C.,greater than or equal to 20° C., or higher. In some embodiments, thedrying step is performed with the coated porous support membrane kept inan environment having a temperature of less than or equal to 150° C.,less than or equal to 80° C., less than or equal to 60° C., or less.Combinations of these ranges are possible. For example, in someembodiments, the drying step is performed with the reacted anionexchange membrane kept in an environment having a temperature of greaterthan or equal to 0° C. and less than or equal to 150° C., greater thanor equal to 0° C. and less than or equal to 80° C., or greater than orequal to 20° C. and less than or equal to 60° C. In some cases, theresulting anion exchange membrane following the reacting step and/or theoptional drying step may be suitable for using in any of a variety ofapplications.

In some embodiments, the anion exchange materials described herein isnot in the form of a membrane. For example, in some embodiments, theanion exchange material may comprise a silica-based ceramic comprisingquaternary ammonium groups covalently bound to the silica-based ceramicas described herein, but without being in the form of a membrane. Insome such cases, the anion exchange material comprises a silica-basedceramic as described herein, but does not necessarily comprise a poroussupport membrane (e.g., upon and/or in which the silica-based ceramic iscoated). One non-limiting example of an anion exchange material that isnot in the form of a membrane is an ion exchange resin. In someembodiments, the anion exchange material is in the form of a bead (e.g.,as an anion exchange bead comprising the silica-based ceramic describedherein), formed, for example, using an emulsion method. As anon-limiting example, FIG. 7 shows a schematic depiction of an anionexchange material 300 comprising a silica-based ceramic 150, with anionexchange material 300 being in the form of a bead, according to someembodiments. In some cases, silica-based ceramic 150 comprisesquaternary ammonium groups covalently bound to the silica-based ceramic,as shown in FIG. 7, according to some embodiments.

In some embodiments, the anion exchange material (e.g., resin) is in theform of a plurality of particles (e.g., a powder) comprising functionalgroups (e.g., silica-based ceramic comprising quaternary ammoniumgroups). In some embodiments, the anion exchange material in the form ofparticles (e.g., a powder) is formed by mechanically breakingsilica-based ceramic described herein (e.g., via any suitable techniqueknown in the art, such as milling). The anion exchange materialparticles may be packed into an ion exchange column and used in any of avariety of applications. In some embodiments, the anion exchangematerial is in the form of a plurality of particles (e.g., a powder)having a mean maximum cross-sectional dimension of greater than or equalto 1 μm, greater than or equal to 2 μm, greater than or equal to 5 μm,greater than or equal to 8 μm, greater than or equal to 10 μm, greaterthan or equal to 15 μm, greater than or equal to 20 μm, greater than orequal to 30 μm, greater than or equal to 50 μm, greater than or equal to75 μm, greater than or equal to 100 μm, greater than or equal to 200 μm,greater than or equal to 500 μm, greater than or equal to 1 mm, orgreater. In some embodiments, the anion exchange material is in the formof a plurality of particles (e.g., a powder) having a mean maximumcross-sectional dimension of less than or equal to 10 mm, less than orequal to 5 mm, less than or equal to 2 mm, less than or equal to 1 mm,less than or equal to 500 μm, less than or equal to 200 μm, less than orequal to 100 μm, less than or equal to 80 μm, less than or equal to 60μm, less than or equal to 50 μm, less than or equal to 40 μm, less thanor equal to 25 μm, or less. Combinations of these ranges are possible.For example, in some embodiments, the anion exchange material is in theform of a plurality of particles (e.g., a powder) having a mean maximumcross-sectional dimension of greater than or equal to 1 μm and less thanor equal to 10 mm.

In some embodiments, an anion exchange material (e.g., a bead,particles) comprising a silica-based ceramic that comprises quaternaryammonium groups covalently bound to the silica-based ceramic isprovided, where the silica-based ceramic comprises a relatively highamount of Si in the silica-based ceramic, as described above. In someembodiments, the silica-based ceramic of the anion exchange material(e.g., a bead) comprises relatively small pores (e.g., pores having anumber average pore diameter of less than or equal to 10 nm or less), asdescribed above. In some embodiments, the anion exchange material (e.g.,in the form of a bead) has a relatively high anion exchange capacity(e.g., greater than 0.01 meq/g of anion exchange membrane).

In some embodiments, an anion exchange material that is not in the formof a membrane can be prepared by reacting a silica-based ceramiccomprising a moiety comprising a leaving group with an amine, where thesilica-based ceramic is not a part of a membrane. For example, in someembodiments an anion exchange membrane comprising a silica-based ceramicthat is in the form of a resin (e.g., comprising a plurality ofparticles or beads) and that comprises quaternary ammonium groups can befabricated using an reacting step similar to that described above withrespect to the anion exchange membranes. For example, some embodimentscomprise exposing a resin comprising a silica-based ceramic comprising amoiety comprising a leaving group (e.g., a substituted alkyl groupcomprising a halo group) to an amine, as described above (e.g.,triethylamine). In some embodiments, the methods further releasing theleaving group and forming a quaternary ammonium group.

In some embodiments, the silica-based ceramic of the resin includes Siin an amount greater than or equal to 6 wt %, greater than or equal to10 wt %, greater than equal to 12 wt %, greater than or equal to 15 wt%, greater than or equal to 17 wt %, greater than or equal to 20 wt %,greater than or equal to 24 wt %, greater than or equal to 30 wt %,greater than or equal to 40 wt %, greater than or equal to 60 wt %, ormore in the silica-based ceramic. In some embodiments, the silica-basedceramic of the resin includes Si in an amount less than or equal to 60wt %, less than or equal to 50 wt %, less than or equal to 47 wt %, lessthan or equal to 40 wt %, less than or equal to 30 wt %, less than orequal to 28 wt %, less than or equal to 26 wt %, less than or equal to24 wt %, less than or equal to 22 wt %, less than or equal to 20 wt %,less than or equal to 17 wt %, or less in the silica-based ceramic.Combinations of these ranges are possible. For example, in someembodiments, the silica-based ceramic comprises Si in an amount greaterthan or equal to 6 wt % and less than or equal to 60 wt %, or greaterthan or equal to 17 wt % and less than or equal to 26 wt % in thesilica-based ceramic of the resin. In some embodiments, the silica-basedceramic of the resin that includes Si in an amount according to theweight percentage ranges above is a resin that comprises a leavinggroup, as described herein.

The anion exchange membranes and materials described herein may be usedin any of a variety of applications. For example, in some embodiments,an anion exchange membrane described herein is used in anelectrochemical application. In some cases, the electrochemicalapplication involves applying a current or voltage in order to, forexample, achieve separation of charged ionic species. Using an anionexchange membrane in an electrochemical application may comprisecontacting the anion exchange membrane with an electrolyte. In someembodiments, using the anion exchange membrane in an electrochemicalapplication may comprise passing current through an electrode inelectrical communication with the electrolyte. For example, in someembodiments, the anion exchange membrane is incorporated into anelectrochemical device (e.g., battery, fuel cell, electrolytic device,etc.). In some such embodiments, the electrochemical apparatus comprisesan electrolyte (e.g., a fluid (liquid) electrolyte or a solidelectrolyte) in contact with the anion exchange membrane and anelectrode in electrical communication with the electrolyte. In someembodiments, the electrochemical apparatus comprises one or more gases(e.g., in contact with the anion exchange membrane) during at least aportion of a charging and/or discharging process (e.g., a fuel cell).Examples of such gas include, but are not limited to, oxygen gas (O₂),hydrogen gas (H₂), carbon dioxide (CO₂), methane (CH₄), and combinationsthereof. In some cases, current is passed through the electrode (e.g.,during an electrochemical reaction) during operation (e.g., a charge ordischarge process) of the electrochemical apparatus. In some embodimentsin which the anion exchange membrane is incorporated into anelectrochemical device, the anion exchange membrane is paired with ananion exchange membrane. In some cases, the anion exchange membrane maybe loaded into a cell, and multiple such cells may be loaded into astack containing more than one anion exchange membrane. Non-limitingexamples of electrochemical applications of the anion exchange membraneinclude electrodialysis, batteries (e.g., redox flow batteries), fuelcells, chemical commodity production (e.g., chloro-alkali production),electrolysis, demineralization, wastewater treatment, chromatography,electrodeionization, desalting (e.g., enhanced oil recovery (EOR)desalting, organic wastewater desalting), chemical contaminant removalfrom wastewater (e.g., ammonia removal from wastewater), water treatment(e.g., mine runoff and tailings treatment), food and beverageproduction, dairy/whey purification, wine stabilization, biologicalpurifications, biochemical production, coating (e.g., electrodepositioncoating), desalination processes, ultra-pure water production, recoveryof plating solutions, recovery of amines, acid recovery processes,caustic recovery processes, and acid removal processes (e.g., removingtartaric acid, malic acid, citric acid). It should be understood that insome cases, the anion exchange membrane can be used in separationsapplications other than those involving the application of an electricfield. For example, in some embodiments, the anion exchange membrane isused for dialysis techniques. One non-limiting example includesdiffusion dialysis (DD). Diffusion dialysis can be used in acid recoveryprocesses (e.g., using a concentration gradient to selectively transportanions).

In some embodiments, an anion exchange membrane described herein is usedas an adsorbent material. For example, in some embodiments, the anionexchange membrane is incorporated into an adsorption apparatus. In somesuch embodiments, the anion exchange membrane is used as an adsorbentmaterial to remove liquid from a gas stream. In some cases, the anionexchange membrane is used as an adsorbent material to remove dissolvedions from a liquid stream (e.g., in an ion exchange process). In someembodiments, using the anion exchange membrane as an adsorbent materialcomprises flowing a fluid through the anion exchange membrane. In somesuch embodiments, using the anion exchange membrane as an adsorbentmaterial further comprises adsorbing a component (e.g., liquid whenremoving liquid from a gas stream, ions when removing ions from a liquidstream) of the fluid that is flowed through the anion exchange membrane.Non-limiting examples of uses of the anion exchange membrane describedherein as an adsorbent material include using the anion exchangemembrane in a pervaporator system, a dehumidifier system, and/or adesiccant or climate control system.

In some embodiments, an anion exchange membrane described herein is usedin a separation application. In some such embodiments, the anionexchange membrane is used in a separation application that comprisesapplying a transmembrane pressure to the anion exchange membrane.Non-limiting examples of separation applications in which the anionexchange membrane is used by applying a transmembrane pressure to theanion exchange membrane include reverse osmosis, microfiltration (e.g.,organic solvent microfiltration, aqueous solvent microfiltration),nanofiltration (e.g., organic solvent nanofiltration, aqueous solventnanofiltration), and ultrafiltration applications. For example, in someembodiments, the anion exchange membrane is incorporated into a reverseosmosis apparatus, a filtration apparatus, or an ultrafiltrationapparatus. Applying a transmembrane pressure to the anion exchangemembrane may, in some cases, comprise contacting the anion exchangemembrane with a liquid (e.g., a liquid solution) and applying ahydrostatic or hydraulic pressure to the liquid such that atransmembrane pressure is applied to the anion exchange membrane. Insome such embodiments, at least a portion of the liquid passes throughthe anion exchange membrane (e.g., from a first side of the anionexchange membrane to a second side of the anion exchange membrane as apermeate).

As mentioned above, in some embodiments, anion exchange materials thatare not in the form of a membrane are also described herein (e.g., inthe form of a resin comprising a plurality of silica-based ceramicparticles or beads). The anion exchange material, which may comprisesilica-based ceramic comprising functional groups as described herein,can be used in any of a variety of applications. For example, in someembodiments, a resin comprising the anion exchange materials describedherein is packed into an ion exchange column. In some such embodiments,the ion exchange column comprising the anion exchange material can beused for waste treatment (e.g., nuclear waste treatment), andpurification processes such as ultrapure water production or protein &biologics purifications.

Definitions of specific functional groups and chemical terms aredescribed in more detail below. For purposes of this invention, thechemical elements are identified in accordance with the Periodic Tableof the Elements, CAS version, Handbook of Chemistry and Physics, 75thEd., inside cover, and specific functional groups are generally definedas described therein. Additionally, general principles of organicchemistry, as well as specific functional moieties and reactivity, aredescribed in Organic Chemistry, Thomas Sorrell, University ScienceBooks, Sausalito: 1999, the entire contents of which are incorporatedherein by reference.

As used herein, the term “aliphatic” refers to alkyl, alkenyl, alkynyl,and carbocyclic groups. Likewise, the term “heteroaliphatic” refers toheteroalkyl, heteroalkenyl, heteroalkynyl, and heterocyclic groups.

The term “alkyl” is given its ordinary meaning in the art and refers tothe radical of saturated aliphatic groups, including straight-chainalkyl groups, branched-chain alkyl groups, cycloalkyl (alicyclic)groups, alkyl substituted cycloalkyl groups, and cycloalkyl substitutedalkyl groups. In some cases, the alkyl group may be a lower alkyl group,i.e., an alkyl group having 1 to 10 carbon atoms (e.g., methyl, ethyl,propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, or decyl). In someembodiments, a straight chain or branched chain alkyl may have 30 orfewer carbon atoms in its backbone, and, in some cases, 20 or fewer. Insome embodiments, a straight chain or branched chain alkyl may have 12or fewer carbon atoms in its backbone (e.g., C₁-C₁₂ for straight chain,C₃-C₁₂ for branched chain), 6 or fewer, or 4 or fewer. Likewise,cycloalkyls may have from 3-10 carbon atoms in their ring structure, or5, 6, or 7 carbons in the ring structure. Examples of alkyl groupsinclude, but are not limited to, methyl, ethyl, propyl, isopropyl,cyclopropyl, butyl, isobutyl, t-butyl, cyclobutyl, hexyl, andcyclohexyl.

The term “alkylene” as used herein refers to a bivalent alkyl group. An“alkylene” group is a polymethylene group, i.e., —(CH₂)_(z)—, wherein zis a positive integer, e.g., from 1 to 20, from 1 to 10, from 1 to 6,from 1 to 4, from 1 to 3, from 1 to 2, or from 2 to 3. A substitutedalkylene chain is a polymethylene group in which one or more methylenehydrogen atoms are replaced with a substituent. Suitable substituentsinclude those described herein for a substituted aliphatic group.Alkylene groups may be cyclic or acyclic, branched or unbranched,substituted or unsubstituted.

Generally, the suffix “-ene” is used to describe a bivalent group. Thus,any of the terms defined herein can be modified with the suffix “-ene”to describe a bivalent version of that moiety. For example, a bivalentcarbocycle is “carbocyclylene”, a bivalent aryl ring is “arylene”, abivalent benzene ring is “phenylene”, a bivalent heterocycle is“heterocyclylene”, a bivalent heteroaryl ring is “heteroarylene”, abivalent alkyl chain is “alkylene”, a bivalent alkenyl chain is“alkenylene”, a bivalent alkynyl chain is “alkynylene”, a bivalentheteroalkyl chain is “heteroalkylene”, a bivalent heteroalkenyl chain is“heteroalkenylene”, a bivalent heteroalkynyl chain is“heteroalkynylene”, and so forth.

The term “aryl” is given its ordinary meaning in the art and refers toaromatic carbocyclic groups, optionally substituted, having a singlering (e.g., phenyl), multiple rings (e.g., biphenyl), or multiple fusedrings in which at least one is aromatic (e.g.,1,2,3,4-tetrahydronaphthyl, naphthyl, anthryl, or phenanthryl). That is,at least one ring may have a conjugated pi electron system, while other,adjoining rings can be cycloalkyls, cycloalkenyls, cycloalkynyls, aryls,and/or heterocyclyls. The aryl group may be optionally substituted, asdescribed herein. Substituents include, but are not limited to, any ofthe previously mentioned substituents, i.e., the substituents recitedfor aliphatic moieties, or for other moieties as disclosed herein,resulting in the formation of a stable compound. In some cases, an arylgroup is a stable mono- or polycyclic unsaturated moiety havingpreferably 3-14 carbon atoms, each of which may be substituted orunsubstituted. “Carbocyclic aryl groups” refer to aryl groups whereinthe ring atoms on the aromatic ring are carbon atoms. Carbocyclic arylgroups include monocyclic carbocyclic aryl groups and polycyclic orfused compounds (e.g., two or more adjacent ring atoms are common to twoadjoining rings) such as naphthyl groups.

The term “arylene,” as used herein refers to an aryl biradical derivedfrom an aryl group, as defined herein, by removal of two hydrogen atoms.Arylene groups may be substituted or unsubstituted. Arylene groupsubstituents include, but are not limited to, any of the substituentsdescribed herein, that result in the formation of a stable moiety.Additionally, arylene groups may be incorporated as a linker group intoan alkylene, alkenylene alkynylene, heteroalkylene, heteroalkenylene, orheteroalkynylene group, as defined herein. Arylene groups may bebranched or unbranched.

The terms “halo” and “halogen” as used herein refer to an atom selectedfrom the group consisting of fluorine, chlorine, bromine, and iodine.

The term “alkoxy” as used herein refers to an alkyl group, as previouslydefined, attached to the parent molecular moiety through an oxygen atomor through a sulfur atom. In certain embodiments, the alkyl groupcontains 1-20 aliphatic carbon atoms. In certain other embodiments, thealkyl group contains 1-10 aliphatic carbon atoms. In yet otherembodiments, the alkyl, alkenyl, and alkynyl groups employed in theinvention contain 1-8 aliphatic carbon atoms. In still otherembodiments, the alkyl group contains 1-6 aliphatic carbon atoms. In yetother embodiments, the alkyl group contains 1-4 aliphatic carbon atoms.Examples of alkoxy, include but are not limited to, methoxy, ethoxy,propoxy, isopropoxy, n-butoxy, t-butoxy, neopentoxy, and n-hexoxy.Examples of thioalkyl include, but are not limited to, methylthio,ethylthio, propylthio, isopropylthio, n-butylthio, and the like. Alkoxygroups may be cyclic or acyclic, branched or unbranched, substituted orunsubstituted.

As used herein, quaternary ammonium groups include quaternary(—N⁺R_(x)R_(y)R_(z)) amine groups (e.g., quaternary ammonium salts),where R_(x), R_(y), and R_(z) are independently an aliphatic, alicyclic,heteroaliphatic, heterocyclic, aryl, or heteroaryl moiety, as definedherein. In some embodiments, quaternary ammonium groups include N⁺(C₁₋₄alkyl)₄ salts.

The term “heterocyclyl” or “heterocyclic” refers to a radical of a 3- to14-membered non-aromatic ring system having ring carbon atoms and 1 to 4ring heteroatoms, wherein each heteroatom is independently selected fromnitrogen, oxygen, and sulfur (“3-14 membered heterocyclyl”). Inheterocyclyl groups that contain one or more nitrogen atoms, the pointof attachment can be a carbon or nitrogen atom, as valency permits. Aheterocyclyl group can either be monocyclic (“monocyclic heterocyclyl”)or polycyclic (e.g., a fused, bridged or spiro ring system such as abicyclic system (“bicyclic heterocyclyl”) or tricyclic system(“tricyclic heterocyclyl”)), and can be saturated or can contain one ormore carbon-carbon double or triple bonds. Heterocyclyl polycyclic ringsystems can include one or more heteroatoms in one or both rings.“Heterocyclyl” also includes ring systems wherein the heterocyclyl ring,as defined above, is fused with one or more carbocyclyl groups whereinthe point of attachment is either on the carbocyclyl or heterocyclylring, or ring systems wherein the heterocyclyl ring, as defined above,is fused with one or more aryl or heteroaryl groups, wherein the pointof attachment is on the heterocyclyl ring, and in such instances, thenumber of ring members continue to designate the number of ring membersin the heterocyclyl ring system. Unless otherwise specified, eachinstance of heterocyclyl is independently unsubstituted (an“unsubstituted heterocyclyl”) or substituted (a “substitutedheterocyclyl”) with one or more substituents. In certain embodiments,the heterocyclyl group is an unsubstituted 3-14 membered heterocyclyl.In certain embodiments, the heterocyclyl group is a substituted 3-14membered heterocyclyl.

The term “heteroaryl” refers to a radical of a 5-14 membered monocyclicor polycyclic (e.g., bicyclic, tricyclic) 4 n+2 aromatic ring system(e.g., having 6, 10, or 14 π electrons shared in a cyclic array) havingring carbon atoms and 1-4 ring heteroatoms provided in the aromatic ringsystem, wherein each heteroatom is independently selected from nitrogen,oxygen, and sulfur (“5-14 membered heteroaryl”). In heteroaryl groupsthat contain one or more nitrogen atoms, the point of attachment can bea carbon or nitrogen atom, as valency permits. Heteroaryl polycyclicring systems can include one or more heteroatoms in one or both rings.“Heteroaryl” includes ring systems wherein the heteroaryl ring, asdefined above, is fused with one or more carbocyclyl or heterocyclylgroups wherein the point of attachment is on the heteroaryl ring, and insuch instances, the number of ring members continue to designate thenumber of ring members in the heteroaryl ring system. “Heteroaryl” alsoincludes ring systems wherein the heteroaryl ring, as defined above, isfused with one or more aryl groups wherein the point of attachment iseither on the aryl or heteroaryl ring, and in such instances, the numberof ring members designates the number of ring members in the fusedpolycyclic (aryl/heteroaryl) ring system. Polycyclic heteroaryl groupswherein one ring does not contain a heteroatom (e.g., indolyl,quinolinyl, carbazolyl, and the like) the point of attachment can be oneither ring, i.e., either the ring bearing a heteroatom (e.g.,2-indolyl) or the ring that does not contain a heteroatom (e.g.,5-indolyl).

As used herein, a “leaving group” (LG) is an art-understood termreferring to a molecular fragment that departs with a pair of electronsin heterolytic bond cleavage, wherein the molecular fragment is an anionor neutral molecule. As used herein, a leaving group can be an atom or agroup capable of being displaced by a nucleophile. See, for example,Smith, March Advanced Organic Chemistry 6th ed. (501-502).

It will be appreciated that the above groups and/or compounds, asdescribed herein, may be optionally substituted with any number ofsubstituents or functional moieties. That is, any of the above groupsmay be optionally substituted. As used herein, the term “substituted” iscontemplated to include all permissible substituents of organiccompounds, “permissible” being in the context of the chemical rules ofvalence known to those of ordinary skill in the art. In general, theterm “substituted” whether proceeded by the term “optionally” or not,and sub stituents contained in formulas of this invention, refer to thereplacement of hydrogen radicals in a given structure with the radicalof a specified substituent. When more than one position in any givenstructure may be substituted with more than one substituent selectedfrom a specified group, the substituent may be either the same ordifferent at every position. It will be understood that “substituted”also includes that the substitution results in a stable compound, e.g.,which does not spontaneously undergo transformation such as byrearrangement, cyclization, elimination, etc. In some cases,“substituted” may generally refer to replacement of a hydrogen with asubstituent as described herein. However, “substituted,” as used herein,does not encompass replacement and/or alteration of a key functionalgroup by which a molecule is identified, e.g., such that the“substituted” functional group becomes, through substitution, adifferent functional group. For example, a “substituted phenyl group”must still comprise the phenyl moiety and cannot be modified bysubstitution, in this definition, to become, e.g., a pyridine ring. In abroad aspect, the permissible substituents include acyclic and cyclic,branched and unbranched, carbocyclic and heterocyclic, aromatic andnonaromatic substituents of organic compounds. Illustrative substituentsinclude, for example, those described herein. The permissiblesubstituents can be one or more and the same or different forappropriate organic compounds. For purposes of this invention, theheteroatoms such as nitrogen may have hydrogen substituents and/or anypermissible substituents of organic compounds described herein whichsatisfy the valencies of the heteroatoms. Furthermore, this invention isnot intended to be limited in any manner by the permissible substituentsof organic compounds. Combinations of substituents and variablesenvisioned by this invention are preferably those that result in theformation of stable compounds useful for the formation of an imagingagent or an imaging agent precursor. The term “stable,” as used herein,preferably refers to compounds which possess stability sufficient toallow manufacture and which maintain the integrity of the compound for asufficient period of time to be detected and preferably for a sufficientperiod of time to be useful for the purposes detailed herein.

Examples of substituents include, but are not limited to, halogen,azide, alkyl, aralkyl, alkenyl, alkynyl, cycloalkyl, hydroxyl, alkoxyl,amino, nitro, sulfhydryl, imino, amido, phosphonate, phosphinate,carbonyl, carboxyl, silyl, ether, alkylthio, sulfonyl, sulfonamido,ketone, aldehyde, ester, heterocyclyl, aromatic or heteroaromaticmoieties, —CF₃, —CN, aryl, aryloxy, perhaloalkoxy, aralkoxy, heteroaryl,heteroaryloxy, heteroarylalkyl, heteroaralkoxy, azido, amino, halide,alkylthio, oxo, acylalkyl, carboxy esters, -carboxamido, acyloxy,aminoalkyl, alkylaminoaryl, alkylaryl, alkylaminoalkyl, alkoxyaryl,arylamino, aralkylamino, alkylsulfonyl, -carboxamidoalkylaryl,-carboxamidoaryl, hydroxyalkyl, haloalkyl, alkylaminoalkylcarboxy-,aminocarboxamidoalkyl-, cyano, alkoxyalkyl, perhaloalkyl,arylalkyloxyalkyl, and the like.

U.S. Provisional Application Ser. No. 62/857,227, filed Jun. 4, 2019,and entitled “CERAMIC ANION EXCHANGE MATERIALS,” is incorporated hereinby reference in its entirety for all purposes.

The following examples are intended to illustrate certain embodiments ofthe present invention, but do not exemplify the full scope of theinvention.

Example 1

This example shows performance characteristics and structural propertiesof an exemplary anion exchange membrane. The anion exchange membranes ofthis example fabricated on a non-woven glass porous support membranewith polymer edging according to the following procedure. The poroussupport membranes were made of borosilicate glass fibers without abinder with an average (mean) pore size of 1 micron. The porous supportmembranes were initially 254 microns thick prior to sol-gelimpregnation. The porous support membranes were initially edged with aUV curable silicone to form a disk with an outer diameter of 35 mm andan inner active area diameter between 10 mm-15 mm. An initial mixturecontaining a 65:35 mass ratio ofTEOS:N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride, 50% inmethanol (TMAPS) was prepared and 0.3 M hydrochloric acid was added toachieve a final water:silicon molar ratio (R) of 2 and 4. This mixturewas agitated and heated to 40° C. for 4 hours before being applied tothe porous support membranes. The coated porous support membranes wereallowed to dry overnight, and for comparison a set with a second coatwas applied following the same procedure. The membranes were soaked in0.5 M NaCl before characterization, where they were found to haveapparent anion permselectivity between 82% and 96% (FIG. 8A); chlorideion conductivities between 0.0008 S/cm and 0.001 S/cm (FIG. 8B); andosmotic water permeances between 2.95 mL·m⁻²·h⁻¹·bar⁻¹ and 5.2mL·m⁻²·h⁻¹·bar⁻¹ (FIG. 8C). Samples prepared similarly had anionexchange capacities between 0.61 meq/g and 0.95 meq/g. SAXS analysis(based on the data and model fit shown in FIG. 8D) showed that themembranes prepared with a molar ratio of water:silicon equal to 4 hadaverage volumetric porosity of 9.5%, average pore radius of 5.1 Å, andaverage log-normal polydispersity index of 0.24.

Example 2

This example shows structural properties of an exemplary anion exchangemembrane. The anion exchange membranes of this example were fabricatedon a non-woven glass porous support membrane with polymer edgingaccording to the following procedure. The porous support membranes weremade of borosilicate glass fibers without a binder with an average(mean) pore size of 1 micron. The porous support membranes wereinitially 254 microns thick prior to sol-gel impregnation. The poroussupport membranes were initially edged with a UV curable silicone toform a disk with an outer diameter of 35 mm and an inner active areadiameter between 10 mm-15 mm. Initial mixtures containing different moleratios (2:1, 4:1, 6:1, 8:1 and 10:1) of TEOS:N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TMAPS), 50% inmethanol were prepared and 0.3 M hydrochloric acid was added to each toachieve a final water:silicon molar ratio (R) of 2. This mixture wasagitated and heated to 40° C. for 4 hours before being applied to theporous support membranes. The coated porous support membranes wereallowed to dry overnight, and a second coat was applied following thesame procedure. SAXS analysis (based on the data and Teubner-Strey modelfit shown in FIG. 9A) showed that the membranes had pores with a radiusranging from 6 Å to 20 Å and volumetric porosity ranging from 4% to 22%.A 6:1 TEOS:TMAPS ratio resulted in a pore radius of 6.1 Å and volumetricporosity of 21%, as shown in FIGS. 9B-9C. FIG. 9D shows the anionexchange capacity for the same membranes.

Example 3

This example shows performance characteristics and structural propertiesof an exemplary anion exchange membrane. The anion exchange membranes ofthis example were fabricated on a non-woven porous polymer supportmembrane of two different thicknesses (190 and 210 microns) with nopolymer edging following a similar procedure to that explained inExample 2, but with a mole ratio of 6:1 for TEOS to TMAPS and an R valueof 2. The mixture was aged for 1 hour at 40° C., and then underwent anadditional open aging step at 100° C. for 30 minutes prior to beingcoated onto the porous support. The coated support was allowed to dryfor 2 hours at room temperature before repeating the coating procedure.This final membrane had 4 coats before being allowed to dry overnight.The anion exchange membranes were soaked in a 0.5 M NaCl solution beforecharacterization. The anion exchange membranes were found to haveapparent anion permselectivities between 92-94% (see FIG. 10A), withchloride ion conductivities between 0.0062 and 0.0079 S/cm (see FIG.10B). Membranes prepared in a similar manner were found to have anaverage anion exchange capacity of 1.4 meq/g.

FIG. 11 shows a cross-sectional SEM image of one of the anion exchangemembranes of this example, In FIG. 11, the cross section includes thenon-woven porous polymer support membrane shown as the dark polymerfibers occupying the center horizontal region of the cross-section. Someof the polymer fibers run horizontally in the plane of the figure, whileothers run in a direction perpendicular to the plane of the figure andappear as circles in the cross-section. The cross section includes thenanoporous silica-based ceramic of the anion exchange membrane as thedense, uniform slab-like lighter-contrast material surrounding on andwithin the porous support membrane.

Example 4

This example shows performance characteristics and structural propertiesof an exemplary anion exchange membrane. The anion exchange membranes ofthis example were fabricated on a non-woven porous glass supportmembrane with polymer edging following a similar procedure to thatexplained in Example 2, but with a mole ratio of 6:1 for TEOS to TMAPSand an R value of 2 and between 2 to 5 coats. The time taken to coat thesol on the samples (between 15 and 60 minutes) and whether the sampleswere dried in an open or closed atmosphere were varied to investigateperformance variations. All samples were soaked in 0.5 M NaCl solutionsprior to characterization. The apparent permselectivities for thesesamples were found to be between 88% and 100% (See FIG. 11A). Thechloride ion conductivities were between 0.0009 S/cm and 0.003 S/cm (SeeFIG. 11B).

FIG. 11C shows a cross-sectional SEM image of one of the anion exchangemembranes of this example, In FIG. 11C, the cross section includes thenon-woven porous polymer support membrane shown as the dark polymerfibers 401 occupying the center horizontal region of the cross-section.Some of the polymer fibers run horizontally in the plane of the figure,while others run in a direction perpendicular to the plane of the figureand appear as circles in the cross-section. The cross section includesthe nanoporous silica-based ceramic of the anion exchange membrane asthe dense, uniform slab-like lighter-contrast material 402 on and withinthe porous support membrane.

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,and/or methods, if such features, systems, articles, materials, and/ormethods are not mutually inconsistent, is included within the scope ofthe present invention.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Other elements may optionallybe present other than the elements specifically identified by the“and/or” clause, whether related or unrelated to those elementsspecifically identified unless clearly indicated to the contrary. Thus,as a non-limiting example, a reference to “A and/or B,” when used inconjunction with open-ended language such as “comprising” can refer, inone embodiment, to A without B (optionally including elements other thanB); in another embodiment, to B without A (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” and the like are to be understoodto be open-ended, i.e., to mean including but not limited to. Only thetransitional phrases “consisting of” and “consisting essentially of”shall be closed or semi-closed transitional phrases, respectively, asset forth in the United States Patent Office Manual of Patent ExaminingProcedures, Section 2111.03.

1. An anion exchange membrane, comprising: a porous support membrane;and a silica-based ceramic that coats at least a portion of the poroussupport membrane, wherein the silica-based ceramic comprises quaternaryammonium groups covalently bound to the silica-based ceramic, andwherein the silica-based ceramic has an average pore diameter of lessthan or equal to 10 nm.
 2. An anion exchange membrane, comprising: aporous support membrane; and a silica-based ceramic that forms a coatingon and/or within the porous support membrane, wherein the silica-basedceramic comprises quaternary ammonium groups covalently bound to thesilica-based ceramic, and wherein the anion exchange membrane has achloride ion conductivity of greater than or equal to 0.00001 S/cm. 3-4.(canceled)
 5. An anion exchange membrane, comprising: a porous supportmembrane; and a silica-based ceramic that forms a coating on and/orwithin the porous support membrane, wherein the silica-based ceramiccomprises quaternary ammonium groups covalently bound to thesilica-based ceramic, and wherein the anion exchange membrane has ananion exchange capacity of greater than or equal to 0.01 meq/g. 6-15.(canceled)
 16. A method for using the anion exchange membrane of claim 1in an electrochemical application, comprising: contacting the anionexchange membrane with an electrolyte; and passing current through anelectrode in electrical communication with the electrolyte. 17-24.(canceled)
 25. The anion exchange membrane claim 1, wherein thequaternary ammonium groups are present in the anion exchange membrane inan amount of 0.01 mmol per gram of the anion exchange membrane. 26-30.(canceled)
 31. The anion exchange membrane of claim 1, wherein thesilica-based ceramic comprises Si in an amount greater than or equal to6 wt % of the silica-based ceramic. 32-33. (canceled)
 34. The anionexchange membrane of claim 1, wherein the anion exchange membrane has alinear expansion of less than or equal to 5%.
 35. The anion exchangemembrane of claim 1, wherein the anion exchange membrane has an anionpermselectivity of greater than or equal to 65%. 36-39. (canceled) 40.The anion exchange membrane of claim 1, wherein an average diameter ofthe pores of the silica-based ceramic is larger when the anion exchangemembrane is in a hydrated state than when the anion exchange membrane isin a dry state by a factor of greater than or equal to 1.1.
 41. Theanion exchange membrane of claim 1, wherein the silica-based ceramiccomprises pores, and wherein an average diameter of the pores of thesilica-based ceramic is larger when the anion exchange membrane is in ahydrated state than when the anion exchange membrane is in a dry stateby a factor of less than or equal to
 5. 42. The anion exchange membraneof claim 1, wherein: when the anion exchange membrane is in a dry state,the pores of the silica-based ceramic fit a model of small anglescattering spectra with intensity (I) as a function of a scatteringvector, q, as follows:${{I(q)} = {\frac{1}{a + {c_{1}q^{2}} + {c_{2}q^{4}}} + {bck}}},$wherein a, c₁, and c₂ are adjustable parameters and bck is backgroundscattering; and when the anion exchange membrane is in a hydrated statethe pores of the silica-based ceramic fit a core-shell model of smallangle scattering spectra with intensity (I) as a function of ascattering vector, q, as follows:$\mspace{79mu} {{{I(q)} = {{{P(q)}{S(q)}} + {b{ck}}}},\mspace{79mu} {{S(q)} = {1 + {\frac{D_{f}{\Gamma \left( {D_{f} - 1} \right)}}{\left. \left\lbrack {1 + {{1/q}\; \xi}} \right)^{2} \right\rbrack^{{({D_{f} - 1})}/2}}\frac{\sin \left\lbrack {\left( {D_{f} - 1} \right){\tan^{- 1}\left( {q\xi} \right)}} \right\rbrack}{\left( {qR_{0}} \right)^{D_{f}}}}}},{{P(q)} = {{\frac{scale}{V_{s}}\left\lbrack {{3{V_{c}\left( {\rho_{c} - \rho_{s}} \right)}\frac{\left\lbrack {{\sin \left( {qr}_{c} \right)} - {{qr}_{c}{\cos \left( {qr}_{c} \right)}}} \right\rbrack}{\left( {qr}_{c} \right)^{3}}} + \mspace{256mu} {3{V_{s}\left( {\rho_{s} - \rho_{block}} \right)}\frac{\left\lbrack {{\sin \left( {qr}_{s} \right)} - {{qr}\; \cos \; \left( {qr}_{s} \right)}} \right\rbrack}{\left( {qr}_{s} \right)^{3}}}} \right\rbrack}^{2} + {bck}}},}$wherein R_(o) is a radius of the building blocks (pores), ρ_(solvent) isa scattering length density of the silica-based ceramic, D_(f) is afractal dimension, is a correlation length, F is the standardmathematical gamma function, scale is a volume fraction of buildingblocks of the measured silica-based ceramic, V_(c) is a volume of thecore, V_(s) is a volume of the shell, ρ_(c) is a scattering lengthdensity of the core, ρ_(s) is a scattering length density of the shell,ρ_(block) is a scattering length density of the pores, r_(c) is a radiusof the core, r_(s) is a radius of the shell, and bck is backgroundscattering. 43-45. (canceled)
 46. The anion exchange membrane of claim1, wherein the silica-based ceramic is derived from the co-condensationof a silicon-containing precursor comprising an ammonium group or amoiety comprising a leaving group.
 47. The anion exchange membrane ofclaim 1, wherein the silica-based ceramic has a silicon to nitrogenmolar ratio of greater than or equal to 1:1.
 48. The anion exchangemembrane of claim 1, wherein the silica-based ceramic has a silicon tonitrogen molar ratio of less than or equal to 120:1. 49-56. (canceled)57. The anion exchange membrane of claim 1, wherein the silica-basedceramic is derived from a mixture comprising a compound having structure(VI):

wherein R⁴, R⁵, and R⁶ are independently chosen fromoptionally-substituted C₁₋₁₈ alkoxy and halo, L is chosen fromoptionally-substituted C₁₋₁₈ alkylene and arylene, and R⁷, R⁸, and R⁹are independently chosen from optionally-substituted C₁₋₁₈ alkyl,cyclyl, and aryl.
 58. The anion exchange membrane of claim 1, whereinthe silica-based ceramic is derived from a mixture comprising a compoundhaving structure (VII):

where A² is independently chosen from hydrogen, methyl, ethyl, propyl,or butyl, n is greater than or equal to 1 and less than or equal to 18,and R¹⁰, R¹¹, and R¹² are independently chosen from methyl, ethyl,propyl, butyl, cyclohexyl, and benzyl.
 59. The anion exchange membraneof claim 1, wherein the silica-based ceramic is derived from a mixturecomprising trimethoxysilylpropyl-N,N,N-trimethylammonium. 60-83.(canceled)
 84. The anion exchange membrane of claim 1, wherein theporous support membrane is in the form of a non-woven fabric or mesh,veil, knit fabric, woven fabric or mesh, open-cell structure, fibril andnode structure, or open-cell foam.
 85. (canceled)
 86. The anion exchangemembrane of claim 1, wherein the porous support membrane comprises apolymeric material comprising polypropylene, polyethylene, polyvinylchloride, polystyrene, polyamide, polyimide, polyacetonitrile,polyvinylacetate, polyethylene glycol, poly ether ether ketone,polysulfone, polyacrylamide, polydimethylsiloxane, polyvinylidenefluoride, polyacrylic acid, polyvinyl alcohol, polyphenylene sulfide,polytetrafluoroethylene, cellulose, microfillibrated cellulose,nanofillibrated cellulose, or combinations or derivatives thereof.87-100. (canceled)
 101. The anion exchange membrane of claim 1, whereinthe porous support membrane has a mechanical burst pressure of greaterthan or equal to 2.0 pounds per square inch (PSI). 102-113. (canceled)